JP2009262132A - Catalyst for purification of exhaust gas and method of purifying exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst which exerts a high methane decomposition capability even at low temperatures in oxidation removal of methane in a combustion exhaust gas containing methane, sulfur oxides and excessive oxygen and a method of oxidation removal of methane in exhaust gas by using it. <P>SOLUTION: The catalyst is for oxidation removal of methane in a combustion exhaust gas containing methane, sulfur oxides and excessive oxygen and includes platinum (a first ingredient), iridium (a second ingredient) and at least one of niobium, tungsten and antimony (a third ingredient) supported in a titanium oxide support. The method is for oxidation removal of methane in a combustion exhaust gas containing methane, sulfur oxides and excessive oxygen and comprises bringing the exhaust gas into contact with the catalyst at 300-500°C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a catalyst for oxidation removal of methane in combustion exhaust gas containing methane, sulfur oxides and excess oxygen, and a method for oxidation removal.

  In the present specification, “containing excess oxygen” means that the gas to be treated (combustion exhaust gas) brought into contact with the catalyst of the present invention completely oxidizes reducing components such as hydrocarbons and carbon monoxide contained therein. It means that an oxidizing component such as oxygen and nitrogen oxide is contained in an amount more than that required for the purpose.

  As a catalyst for removing oxidation of hydrocarbons in exhaust gas, it is known that a catalyst supporting a platinum group metal such as platinum or palladium exhibits high performance. For example, an exhaust gas purifying catalyst having platinum and palladium supported on an alumina carrier is disclosed (see Patent Document 1). However, even if such a catalyst is used, methane has high chemical stability when the main component of hydrocarbons in the exhaust gas is methane, such as methane fermentation gas or natural gas combustion exhaust gas. In addition, there is a problem that a sufficient methane removal rate is not achieved.

  Furthermore, since the combustion exhaust gas necessarily contains a reaction inhibiting substance such as a sulfur oxide derived from the sulfur compound contained in the fuel, the reaction inhibiting substance is deposited on the catalyst surface, so that the catalyst It is inevitable that the activity decreases significantly with time.

  For example, Lampert et al. Show that when methane oxidation is carried out using a palladium catalyst, only 0.1 ppm of sulfur dioxide is present and its catalytic activity is almost lost within a few hours. It has been clarified that the presence of sulfur oxide has a significant adverse effect on the catalytic activity (see Non-Patent Document 1).

  Furthermore, 7 g / l or more of palladium and 3 to 20 g / l of platinum were supported on the honeycomb base material via an alumina carrier as a catalyst for oxidizing low-concentration hydrocarbons contained in exhaust gas in which an excessive amount of oxygen was present. A catalyst is also disclosed (see Patent Document 2). However, even if this catalyst is used, long-term durability is not sufficient, and deterioration of the catalyst activity over time is unavoidable under conditions where sulfur oxides coexist.

  Thus, the big problem of the prior art is that a high removal rate cannot be obtained with respect to methane, and further, the removal rate is greatly reduced under the condition where sulfur oxides coexist.

  In view of such a situation, it is disclosed that a catalyst in which palladium or palladium and platinum are supported on a zirconium oxide support continues to maintain high methane oxidation activity even in the presence of sulfur oxide (see Patent Document 3). ). However, since this catalyst has a low methane oxidation activity particularly in a low temperature range of about 400 ° C. or less, a large amount of catalyst is required to ensure sufficient performance at a low temperature.

  In addition, an unburned hydrocarbon oxidation catalyst in exhaust gas in which platinum and palladium are supported on a titanium oxide support has been proposed (see Patent Document 4), but this catalyst is also particularly in a low temperature range of about 400 ° C. or lower. Methane oxidation activity is not enough.

  While it was theorized that palladium is effective for the oxidation of methane (see Non-Patent Document 2 and Non-Patent Document 3), it does not contain palladium and only platinum is supported on a support made of tin oxide. There is also a document showing that the catalyst is active in removing methane from combustion exhaust gas by oxidation (see Patent Document 5). However, this catalyst does not have sufficient methane removal performance at 400 ° C. or lower, and requires a large amount of expensive platinum.

A catalyst for purifying hydrocarbons in combustion exhaust gas containing methane and containing oxygen excessively, comprising zirconium oxide supporting at least one selected from the group consisting of platinum, palladium, rhodium and ruthenium and iridium. It is also disclosed that a catalyst having a specific surface area of ² to 60 m ² / g continues to maintain high methane oxidation activity even at a low temperature of about 400 ° C. in the presence of sulfur oxide (patent document) 6). However, this catalyst has a practical problem in that it requires a relatively large amount of iridium, which is a very rare noble metal.

  In addition, a catalyst is proposed in which iridium is supported as a co-catalyst on a catalyst in which platinum is supported on tin oxide, and methane in combustion exhaust gas containing sulfur oxide is oxidized and removed at a low temperature range (see Patent Document 7). However, this catalyst does not have sufficient methane removal performance below 400 ° C.

  In addition, in order to decompose and remove NOx components contained in the combustion exhaust gas of gas fuel, a porous carrier made of one or more of alumina, zirconium oxide, and titanium oxide is used with one or more of iridium, platinum, and rhodium. A catalyst for removing NOx carrying a plurality of species has been proposed (see Patent Document 8). However, this document only shows NOx removal performance, and does not teach any removal rate of hydrocarbons. What is the possibility of oxidative decomposition of the most difficult-to-decompose methane among hydrocarbons? I did not suggest.

  A method for producing an exhaust gas purifying catalyst in which at least one of platinum and rhodium and at least one of iridium and ruthenium are supported on an inorganic support such as activated alumina by a specific method using citric acid. Is disclosed (see Patent Document 9). According to this document, iridium and / or ruthenium form a solid solution having a high melting point with platinum and / or rhodium, so that the heat resistance of the obtained catalyst is improved. However, this document only shows that the NOx conversion rate of the obtained catalyst has been improved, and does not teach any oxidative decomposition of methane, which is particularly difficult to decompose among the hydrocarbons contained in the exhaust gas. .

  There has been proposed a lean burn engine exhaust gas denitration catalyst in which iridium is supported on various supports such as alumina, silica, zirconium oxide, and titanium oxide (see Patent Document 10). However, this document also does not show recognition that methane is particularly difficult to decompose among various hydrocarbons present in the exhaust gas. Therefore, it has not been clarified at all about how methane can be efficiently oxidized and decomposed.

Japanese Patent Laid-Open No. 51-106691 JP-A-8-332392 JP-A-11-319559 JP 2000-254500 A Japanese Patent Laid-Open No. 2004-351236 International Publication WO2002 / 040152 JP 2006-272079 A Japanese Patent Laid-Open No. 3-293035 Japanese Patent Laid-Open No. 3-98644 Japanese Unexamined Patent Publication No. 7-80315

Applied Catalysis B: Environmental, Vol. 14, pp. 211-223 (1997) Industrial and Engineering Chemistry, Vol. 53, 809-812 (1961) Industrial and Engineering Chemistry Product Research and Development, Vol. 19, pp. 293-298 (1980)

  An object of the present invention is to provide a catalyst that exhibits high methane resolution even at a low temperature in the oxidation removal of methane in combustion exhaust gas containing excessive oxygen, and a method for oxidizing and removing methane in exhaust gas using this catalyst. There is.

The present invention provides an exhaust gas purification catalyst, a production method thereof, and an exhaust gas purification method as described below.
Item 1. A catalyst for oxidizing and removing methane in combustion exhaust gas containing methane, sulfur oxides and excess oxygen, including titanium oxide as a first component, iridium as a second component, niobium, tungsten as a third component And a catalyst carrying at least one selected from the group consisting of antimony.
Item 2. Item 2. The catalyst according to Item 1, wherein the supported amount of platinum is 0.5 to 20% by mass ratio to titanium oxide.
Item 3. Item 3. The catalyst according to Item 1 or 2, wherein the supported amount of platinum and iridium is in the range of platinum / iridium = 0.2 to 9 by mass ratio.
Item 4. The supported amount of platinum and at least one selected from the group consisting of niobium, tungsten and antimony is in the range of platinum / (at least one selected from the group consisting of niobium, tungsten and antimony) = 0.2 to 9 in mass ratio. Item 4. The catalyst according to any one of Items 1 to 3.
Item 5. A method for producing a catalyst comprising a titanium oxide support supporting at least one selected from the group consisting of platinum as a first component, iridium as a second component, niobium, tungsten and antimony as a third component, comprising a platinum compound, Item 1-4, wherein a mixed aqueous solution of an iridium compound and at least one compound selected from the group consisting of a niobium compound, a tungsten compound, and an antimony compound is impregnated and supported on a titanium oxide carrier, and dried and fired. A process for producing the catalyst according to any one of the above.
Item 6. A method for oxidizing and removing methane in combustion exhaust gas containing methane, sulfur oxides and excess oxygen, wherein the exhaust gas is brought into contact with the catalyst according to any one of Items 1 to 4 at a temperature of 300 to 500 ° C. Method.

  Hereinafter, the present invention will be described in detail.

  The catalyst of the present invention is a catalyst for oxidizing and removing methane in combustion exhaust gas, and includes at least one selected from the group consisting of niobium, tungsten and antimony together with titanium oxide as a carrier, platinum and iridium as catalytic active components. It is characterized by carrying a seed.

  When the surface area of titanium oxide as a support is too small, the catalytically active component cannot be kept highly dispersed. On the other hand, when the surface area is too large, the thermal stability of the titanium oxide is not sufficient, and the titanium oxide itself may be sintered during the use of the catalyst.

The specific surface area of titanium oxide (referred to herein as the specific surface area by the BET method) is usually about ^{2 to} 90 m ² / g, and preferably about 5 to 60 m ² / g. The crystal form of titanium oxide is preferably anatase type, but may contain 25% or less of rutile type titanium oxide on a mass basis. A known method such as X-ray diffraction measurement can be applied to the measurement of the crystal phase content ratio. Such a titanium oxide may be a commercially available titanium oxide for a catalyst carrier as it is, or can be prepared by a method such as firing at 550 ° C. to 700 ° C. in an oxidizing atmosphere such as air.

  The catalyst carrier may contain a small amount of components other than titanium oxide such as alumina and silica in order to improve adhesion to a support such as cordierite and sinterability, but these components are based on mass. It is desirable not to exceed 2%.

  When the amount of the catalytically active component supported on the titanium oxide is too small, the catalytic activity is low, whereas when it is too large, the particle size becomes large and the supported catalytically active component is not effectively used.

  The supported amount of platinum is preferably about 0.5 to 20% by mass ratio with respect to titanium oxide, and more preferably about 0.5 to 5%. The supported amount of iridium is preferably about 0.1 to 20% by mass ratio with respect to titanium oxide, and more preferably about 0.2 to 5%. The ratio of the supported amount of platinum and iridium is preferably about 0.2 to 9 and more preferably about 0.5 to 4 by mass ratio of Pt / Ir. The supported amount of at least one selected from the group consisting of niobium, tungsten and antimony is preferably about 0.1 to 20%, more preferably about 0.2 to 5% in terms of mass ratio to titanium oxide. The supported amount ratio of platinum and at least one selected from the group consisting of niobium, tungsten and antimony is 0.2 to 9 in terms of mass ratio of platinum / (at least one selected from the group consisting of niobium, tungsten and antimony). Is preferably about 0.4, and more preferably about 0.4 to 2.

  The catalyst of the present invention, for example, impregnates and supports a titanium oxide carrier with a mixed aqueous solution of at least one compound selected from the group consisting of platinum compounds, iridium compounds, niobium compounds, tungsten compounds, and antimony compounds, and is dried. Obtained by firing.

  The impregnation operation may be performed using an aqueous solution prepared by dissolving a water-soluble compound such as a chloro complex, an ammine complex, or nitrate in pure water, or an organic metal compound such as an acetylacetonato complex may be used as an organic material such as acetone. You may carry out using the organic-solvent solution melt | dissolved in the solvent.

  Examples of the water-soluble compound include chloroiridate (hexachloroiridate), hexaammineiridium nitrate, chloroplatinic acid, tetraammineplatinum nitrate, dinitrodiammineplatinum, niobium chloride, ammonium tungstate, and antimony chloride. If the solubility is low and the desired concentration cannot be obtained by dissolving in pure water, dilute nitric acid, dilute hydrochloric acid, or aqueous ammonia may be added to increase the solubility.

  Examples of the organometallic compound include tris (acetylacetonato) iridium and bis (acetylacetonato) platinum.

  The impregnation time is not particularly limited as long as a predetermined loading amount is ensured, but is usually about 1 to 50 hours, preferably about 3 to 20 hours.

  Next, the titanium oxide supporting a predetermined metal component is evaporated or dried or dried as necessary, and then fired.

  Firing may be performed under air circulation. Or you may carry out in distribution | circulation of oxidizing gas, such as the gas which mixed air or oxygen, and inert gas, such as nitrogen, suitably.

  If the firing temperature is too high, grain growth of the supported metal proceeds and high activity cannot be obtained. On the other hand, if it is too low, the calcination is not performed sufficiently, so that the metal particles supported during the use of the catalyst may become coarse and stable activity may not be obtained. Therefore, in order to stably obtain high catalytic activity, the calcination temperature is preferably about 450 to 650 ° C, more preferably about 500 to 600 ° C.

  The firing time is not particularly limited, but is usually about 1 to 50 hours, preferably about 3 to 20 hours.

  The catalyst of the present invention may be used after being molded into an arbitrary shape such as pellets or honeycombs, or may be used by wash coating on a refractory honeycomb. Preferably, the refractory honeycomb is wash coated.

  When wash-coating on a fire-resistant honeycomb, the catalyst prepared by the above method may be slurry-coated and washed, or after titanium oxide is washed on the fire-resistant honeycomb beforehand, the impregnation described above may be performed. The active ingredient may be supported according to the technique. In either case, a binder can be added as necessary.

The specific surface area of the catalyst of the present invention is usually about ^{2 to} 90 m ² / g, preferably about 5 to 60 m ² / g.

  The exhaust gas purification method of the present invention is a treatment target for combustion exhaust gas containing methane, sulfur oxides, and excess oxygen. In addition to methane, the combustion exhaust gas may contain lower hydrocarbons such as ethane and propane, carbon monoxide, and oxygen-containing combustible components. Since these are easily decomposable as compared with methane, they can be easily oxidized and removed simultaneously with methane by the method of the present invention.

  The concentration of flammable components in the exhaust gas is not particularly limited, but if it is too high, an extreme temperature rise occurs in the catalyst layer, which may adversely affect the durability of the catalyst. The following is preferable.

  The method for oxidizing and removing methane in exhaust gas according to the present invention is characterized by using the catalyst obtained as described above.

When the amount of the catalyst used is too small, an effective purification rate cannot be obtained. Therefore, it is preferable to use an amount that gives a space velocity per gas hour (GHSV) of 200,000 h ⁻¹ or less. On the other hand, the lower the gas hourly space velocity (GHSV), the greater the amount of catalyst, so the purification rate improves, but if GHSV is too low, it is economically disadvantageous and pressure loss in the catalyst layer Becomes larger. Therefore, the lower limit of GHSV may preferably be about 1,000 h ^-1, and more preferably about 5,000h ^-1.

  The oxygen concentration in the exhaust gas, which is the gas to be treated, is not particularly limited as long as it contains oxygen in excess, but it is about 2% or more (more preferably about 5% or more) on a volume basis and has a reducing property consisting of hydrocarbons and the like It is preferred that there be about 5 times or more (more preferably about 10 times or more) of oxygen equivalent to the oxidation equivalent of the components.

  When the oxygen concentration in the exhaust gas is extremely low, the reaction rate may decrease. Therefore, a required amount of air, excess oxygen exhaust gas, or the like may be mixed in advance.

  The catalyst for removing oxidation of methane in the exhaust gas of the present invention has high activity. However, when the exhaust gas treatment temperature is too low, the activity is lowered and a desired methane conversion rate cannot be obtained. On the other hand, when the treatment temperature is too high, the durability of the catalyst may deteriorate.

  The temperature of the catalyst layer is usually about 300 to 500 ° C, preferably about 300 to 450 ° C.

  In addition, when the concentration of hydrocarbons in the gas to be treated is extremely high, a rapid reaction occurs in the catalyst layer, which adversely affects the durability of the catalyst, so the temperature rise in the catalyst layer is usually about 150 ° C. or less, It is preferable to use it under conditions of about 100 ° C. or less.

  The combustion exhaust gas normally contains about 5 to 15% of water vapor, but according to the present invention, effective methane oxidation removal is achieved even for the exhaust gas containing water vapor.

  The combustion exhaust gas usually contains sulfur oxides that significantly reduce the catalyst activity. However, the catalyst of the present invention exhibits a particularly high resistance to the activity reduction caused by sulfur oxides, so that 0.1% by volume. Even when about 30 ppm of sulfur oxide is contained, the methane conversion is not substantially affected.

  Since the catalyst of the present invention exhibits very excellent resistance to activity inhibition by water vapor and sulfur oxides, even in exhaust gas containing a large amount of water vapor and containing sulfur oxide like combustion exhaust gas, high methane Exhibits oxidative activity.

  Further, since the catalyst of the present invention exhibits high activity even at a low temperature, the amount of expensive noble metal used can be reduced and the economy is excellent.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated in detail, this invention is not limited to these Examples.

Example 1
Commercially available titanium oxide (MC-50 manufactured by Ishihara Sangyo Co., Ltd., specific surface area 62 m ² / g) was calcined in air at 700 ° C. for 4 hours to obtain calcined titanium oxide. Dinitrodiammineplatinum (cis-Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ) (0.109 g) and iridium chloride (IrCl ₃ · xH ₂ O, containing 54.8% as Ir) (0.027 g) were added to concentrated nitric acid (0.50 ml) was added and dissolved by heating, and then distilled water (10 ml) was added. Hydrochloric acid (0.50 ml) was added to antimony chloride (SbCl ₃ ) (0.112 g) and dissolved by heating, and distilled water (10 ml) was added. Subsequently, after mixing each said aqueous solution, the said baked titanium oxide (3.0 g) was immersed. After evaporating to dryness and drying at 60 ° C., it was calcined in air at 500 ° C. for 2 hours to obtain a 2% Pt-0.5% Ir-2% Sb / titanium oxide catalyst.

Example 2
Commercially available titanium oxide (MC-50 manufactured by Ishihara Sangyo Co., Ltd., specific surface area 62 m ² / g) was calcined in air at 700 ° C. for 4 hours to obtain calcined titanium oxide. Dinitrodiammineplatinum (cis-Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ) (0.109 g) and iridium chloride (IrCl ₃ · xH ₂ O, containing 54.8% as Ir) (0.027 g) were added to concentrated nitric acid (0.50 ml) was added and dissolved by heating, and then distilled water (10 ml) was added. After heated and dissolved by addition of hydrochloric acid (0.50 ml) in ammonium tungstate pentahydrate _{((NH 4) 10 W 12} O 41 · 5H 2 O) (0.0975g), was added distilled water (10 ml). Subsequently, after mixing said each aqueous solution, the said baked titanium oxide (3.0g) was immersed. After evaporating to dryness and drying at 60 ° C., it was calcined in air at 500 ° C. for 2 hours to obtain a 2% Pt-0.5% Ir-2% W / titanium oxide catalyst.

Example 3
Commercially available titanium oxide (MC-50 manufactured by Ishihara Sangyo Co., Ltd., specific surface area 62 m ² / g) was calcined in air at 700 ° C. for 4 hours to obtain calcined titanium oxide. Dinitrodiammineplatinum (cis-Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ) (0.109 g), iridium chloride (IrCl ₃ · xH ₂ O, containing 54.8% as Ir) (0.027 g) and niobium chloride (NbCl ₅ ) Concentrated nitric acid (0.50 ml) was added to each (0.175 g) and dissolved by heating, and then distilled water (10 ml) was added. Subsequently, after mixing each aqueous solution, the said baked titanium oxide (3.0 g) was immersed. After evaporating to dryness and drying at 60 ° C., it was calcined in air at 500 ° C. for 2 hours to obtain a 2% Pt-0.5% Ir-2% Nb / titanium oxide catalyst.

Comparative Example 1
Commercially available titanium oxide (MC-50 manufactured by Ishihara Sangyo Co., Ltd., specific surface area 62 m ² / g) was calcined in air at 700 ° C. for 4 hours to obtain calcined titanium oxide. Dinitrodiammineplatinum (cis-Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ) (0.109 g) is added with concentrated nitric acid (0.50 ml), heated and dissolved, then distilled water (10 ml) is added, and the above-mentioned calcined titanium oxide (3.0 g) was immersed. After evaporating to dryness and drying at 60 ° C., it was calcined in air at 500 ° C. for 2 hours to obtain a 2% Pt / titanium oxide catalyst.

Comparative Example 2
Commercially available titanium oxide (MC-50 manufactured by Ishihara Sangyo Co., Ltd., specific surface area 62 m ² / g) was calcined in air at 700 ° C. for 4 hours to obtain calcined titanium oxide. Dinitrodiammineplatinum (cis-Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ) (0.109 g) and iridium chloride (IrCl ₃ · xH ₂ O, containing 54.8% as Ir) (0.027 g) were added to concentrated nitric acid (0.50 ml) was added and dissolved by heating, and then distilled water (10 ml) was added and mixed, and the calcined titanium oxide (3.0 g) was immersed therein. After evaporating to dryness and drying at 60 ° C., it was calcined in air at 500 ° C. for 2 hours to obtain a 2% Pt-0.5% Ir / titanium oxide catalyst.

[Activity evaluation test 1]
Each of the catalysts prepared in Examples 1 to 3 and Comparative Examples 1 and 2 was subjected to tableting, and 2.0 ml (about 1.4 g) of each molded body was filled in a quartz reaction tube (inner diameter 20 mm). Next, a gas having a composition consisting of 1,000 ppm of methane, 10% oxygen, 10% water vapor (both based on volume) and the balance nitrogen is circulated in the reaction tube under the condition of GHSV (space velocity per gas hour) 40,000h- ^1. The methane conversion at catalyst layer temperatures of 300 ° C., 350 ° C., 400 ° C. and 450 ° C. was measured (initial conversion rate). The gas composition before and after the reaction layer was measured by a gas chromatograph having a flame ionization detector. Thereafter, while maintaining the catalyst layer temperature at 450 ° C., 3 ppm of sulfur dioxide was added to the reaction gas to continue the reaction. At each time point after 20 hours and 45 hours, the catalyst layer temperature was 450 ° C., 400 ° C., The methane conversion at 350 ° C. and 300 ° C. was measured similarly.

Table 1 shows the measurement results of methane conversion (%). Here, the methane conversion is a value obtained by the following equation.
CH ₄ conversion (%) = 100 × (1−CH ₄ -OUT / CH ₄ -in)
In the formula, “CH ₄ -OUT” indicates the methane concentration at the catalyst layer outlet, and “CH ₄ -in” indicates the methane concentration at the catalyst layer inlet.

  The catalysts of Examples 1 to 3 exhibit high performance even at a low temperature and are not substantially inhibited by the sulfur compound. Moreover, the activity after 45 hours is not different from the initial activity. By supporting at least one selected from the group consisting of platinum, iridium, and antimony, tungsten and niobium on the titanium oxide support, the methane conversion increases and high catalytic activity is maintained over a long period of time.

Example 4
Commercially available titanium oxide (MC-50 manufactured by Ishihara Sangyo Co., Ltd., specific surface area 62 m ² / g) was calcined in air at 700 ° C. for 4 hours to obtain calcined titanium oxide. Dinitrodiammineplatinum (cis-Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ) (0.055 g) and iridium chloride (IrCl ₃ · xH ₂ O, containing 54.8% as Ir) (0.027 g) were added to concentrated nitric acid (0.50 ml) was added and dissolved by heating, and then distilled water (10 ml) was added. Hydrochloric acid (0.50 ml) was added to antimony chloride (SbCl ₃ ) (0.112 g) and dissolved by heating, and distilled water (10 ml) was added. Subsequently, after mixing each said aqueous solution, the said baked titanium oxide (3.0 g) was immersed. After evaporating to dryness and drying at 60 ° C., it was calcined in air at 500 ° C. for 2 hours to obtain a 1% Pt-0.5% Ir-2% Sb / titanium oxide catalyst.

Example 5
Commercially available titanium oxide (MC-50 manufactured by Ishihara Sangyo Co., Ltd., specific surface area 62 m ² / g) was calcined in air at 700 ° C. for 4 hours to obtain calcined titanium oxide. Dinitrodiammineplatinum (cis-Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ) (0.027 g) and iridium chloride (IrCl ₃ · xH ₂ O, containing 54.8% as Ir) (0.027 g) were added to concentrated nitric acid (0.50 ml) was added and dissolved by heating, and then distilled water (10 ml) was added. Hydrochloric acid (0.50 ml) was added to antimony chloride (SbCl ₃ ) (0.112 g) and dissolved by heating, and distilled water (10 ml) was added. Subsequently, after mixing said each aqueous solution, the said baked titanium oxide (3.0g) was immersed. After evaporating to dryness and drying at 60 ° C., the mixture was calcined at 500 ° C. for 2 hours in air to obtain a 0.5% Pt-0.5% Ir-2% Sb / titanium oxide catalyst.

Example 6
Commercially available titanium oxide (MC-50 manufactured by Ishihara Sangyo Co., Ltd., specific surface area 62 m ² / g) was calcined in air at 700 ° C. for 4 hours to obtain calcined titanium oxide. Dinitrodiammineplatinum (cis-Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ) (0.109 g) and iridium chloride (IrCl ₃ xH ₂ O, containing 54.8% as Ir) (0.108 g) were added to concentrated nitric acid (0.50 ml) was added and dissolved by heating, and then distilled water (10 ml) was added. Hydrochloric acid (0.50 ml) was added to antimony chloride (SbCl ₃ ) (0.112 g) and dissolved by heating, and distilled water (10 ml) was added. Subsequently, after mixing said each aqueous solution, the said baked titanium oxide (3.0g) was immersed. After evaporating to dryness and drying at 60 ° C., it was calcined in air at 500 ° C. for 2 hours to obtain a 2% Pt-2% Ir-2% Sb / titanium oxide catalyst.

Example 7
Commercially available titanium oxide (MC-50 manufactured by Ishihara Sangyo Co., Ltd., specific surface area 62 m ² / g) was calcined in air at 700 ° C. for 4 hours to obtain calcined titanium oxide. Dinitrodiammineplatinum (cis-Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ) (0.109 g) and iridium chloride (IrCl ₃ · xH ₂ O, containing 54.8% as Ir) (0.216 g) were added to concentrated nitric acid (0.50 ml) was added and dissolved by heating, and then distilled water (10 ml) was added. Hydrochloric acid (0.50 ml) was added to antimony chloride (SbCl ₃ ) (0.112 g) and dissolved by heating, and distilled water (10 ml) was added. Subsequently, after mixing said each aqueous solution, the said baked titanium oxide (3.0g) was immersed. After evaporating to dryness and drying at 60 ° C., the mixture was calcined in air at 500 ° C. for 2 hours to obtain a 2% Pt-4% Ir-2% Sb / titanium oxide catalyst.

Example 8
Commercially available titanium oxide (MC-50 manufactured by Ishihara Sangyo Co., Ltd., specific surface area 62 m ² / g) was calcined in air at 700 ° C. for 4 hours to obtain calcined titanium oxide. Dinitrodiammineplatinum (cis-Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ) (0.109 g) and iridium chloride (IrCl ₃ · xH ₂ O, containing 54.8% as Ir) (0.027 g) were added to concentrated nitric acid (0.50 ml) was added and dissolved by heating, and then distilled water (10 ml) was added. Hydrochloric acid (0.50 ml) was added to antimony chloride (SbCl ₃ ) (0.056 g) and dissolved by heating, and distilled water (10 ml) was added. Subsequently, after mixing said each aqueous solution, the said baked titanium oxide (3.0g) was immersed. After evaporating to dryness and drying at 60 ° C., it was calcined in air at 500 ° C. for 2 hours to obtain a 2% Pt-0.5% Ir-1% Sb / titanium oxide catalyst.

Example 9
Commercially available titanium oxide (MC-50 manufactured by Ishihara Sangyo Co., Ltd., specific surface area 62 m ² / g) was calcined in air at 700 ° C. for 4 hours to obtain calcined titanium oxide. Dinitrodiammineplatinum (cis-Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ) (0.109 g) and iridium chloride (IrCl ₃ · xH ₂ O, containing 54.8% as Ir) (0.027 g) were added to concentrated nitric acid (0.50 ml) was added and dissolved by heating, and then distilled water (10 ml) was added. Hydrochloric acid (0.50 ml) was added to antimony chloride (SbCl ₃ ) (0.280 g) and dissolved by heating, and distilled water (10 ml) was added. Subsequently, after mixing said each aqueous solution, the said baked titanium oxide (3.0g) was immersed. After evaporating to dryness and drying at 60 ° C., the mixture was calcined in air at 500 ° C. for 2 hours to obtain a 2% Pt-0.5% Ir-5% Sb / titanium oxide catalyst.

Comparative Example 3
Commercially available titanium oxide (MC-50 manufactured by Ishihara Sangyo Co., Ltd., specific surface area 62 m ² / g) was calcined in air at 700 ° C. for 4 hours to obtain calcined titanium oxide. Hydrochloric acid (0.50 ml) was added to antimony chloride (SbCl ₃ ) (0.112 g) and dissolved by heating, distilled water (10 ml) was added, and the calcined titanium oxide (3.0 g) was immersed therein. After evaporating to dryness and drying at 60 ° C., the mixture was calcined in air at 500 ° C. for 2 hours to obtain 2% Sb / titanium oxide. Dinitrodiammineplatinum (cis-Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ) (0.109 g) and iridium chloride (IrCl ₃ · xH ₂ O, containing 54.8% as Ir) (0.027 g) were added to concentrated nitric acid (0.50 ml) was added and dissolved by heating, and then distilled water (10 ml) was added. Next, after mixing each aqueous solution, the 2% Sb / titanium oxide was immersed. After evaporating to dryness and drying at 60 ° C., it was calcined in air at 500 ° C. for 2 hours to obtain a 2% Pt-0.5% Ir-2% Sb / titanium oxide catalyst.

[Activity evaluation test 2]
The performance of the catalysts prepared in Examples 4 to 9 and Comparative Example 3 was evaluated in the same manner as in the activity evaluation test 1. Table 2 shows the measurement results of methane conversion (%).

  In the catalysts of Examples 4 to 9, since the supported amount of platinum with respect to titanium oxide, the ratio of the supported amount of platinum and iridium, and the ratio of the supported amount of platinum and antimony are within specific preferred ranges, As a result, high methane oxidation activity was obtained.

  The catalyst of Comparative Example 3 was impregnated and supported with an aqueous solution of an antimony compound on a titanium oxide support, dried and calcined, and then mixed with an aqueous solution of a platinum compound and an iridium compound was impregnated and supported on the titanium oxide support with antimony, and was dried and calcined. Thus, the methane conversion was lower than when the reaction was carried out using the catalyst of Example 1. This means that a catalyst obtained by impregnating and supporting a mixed aqueous solution of a platinum compound, an iridium compound, and an antimony compound on a titanium oxide carrier, and drying and calcining can provide a stable and high methane oxidation activity. Is shown.

  According to the present invention, it becomes possible to stably oxidize and remove methane in combustion exhaust gas, so that it contains sulfur oxides such as combustion exhaust gas such as methane fermentation gas and natural gas city gas, and various process gases. By treating the exhaust gas to be treated by the method of the present invention, methane contained in the exhaust gas is oxidized and removed, and the reaction heat can be recovered and effectively used as energy, and also contributes to the improvement of the global environment.

Claims (6)

  A catalyst for oxidizing and removing methane in combustion exhaust gas containing methane, sulfur oxides and excess oxygen, including titanium oxide as a first component, iridium as a second component, niobium, tungsten as a third component And a catalyst carrying at least one selected from the group consisting of antimony.   The catalyst according to claim 1, wherein the supported amount of platinum is 0.5 to 20% by mass ratio with respect to titanium oxide.   The catalyst according to claim 1 or 2, wherein the supported amount of platinum and iridium is in the range of platinum / iridium = 0.2 to 9 by mass ratio.   The supported amount of platinum and at least one selected from the group consisting of niobium, tungsten and antimony is in the range of platinum / (at least one selected from the group consisting of niobium, tungsten and antimony) = 0.2 to 9 in mass ratio. The catalyst according to any one of claims 1 to 3.   A method for producing a catalyst comprising a titanium oxide support supporting at least one selected from the group consisting of platinum as a first component, iridium as a second component, niobium, tungsten and antimony as a third component, comprising a platinum compound, An iridium compound and a mixed aqueous solution of at least one compound selected from the group consisting of a niobium compound, a tungsten compound, and an antimony compound are impregnated and supported on a titanium oxide carrier, and dried and fired. 5. A method for producing the catalyst according to any one of 4 above.   A method for oxidizing and removing methane in combustion exhaust gas containing methane, sulfur oxides and excess oxygen, wherein the exhaust gas is contacted with the catalyst according to any one of claims 1 to 4 at a temperature of 300 to 500 ° C. How to make.