JP4120332B2 - Catalyst for selective oxidation of carbon monoxide and oxidation method - Google Patents

Description

【００６６】
この表中に示す酸素転化率とは、改質ガス中に存在する酸素分子のうち、何％の酸素分子が消費したかを示す指標であり、ＣＯ転化率とは、改質ガス中の一酸化炭素分子のうち、何％の一酸化炭素分子が消費されたかを示す指標である。
【００６７】
【発明の効果】
一酸化炭素を選択的に酸化する方法において、結晶子の小さい触媒を用いることにより、触媒活性を大きく向上することが出来た。また、改質ガスの成分に含まれる一酸化炭素濃度が１％を越えていても、あるいは二酸化炭素濃度共存下においても活性の高い一酸化炭素選択酸化用触媒を得ることが出来た。
【図面の簡単な説明】
【図１】実施例中にあるゼオライト１（モルデナイト）のＸ線回折図である。
【図２】実施例中にあるゼオライト２（モルデナイト）のＸ線回折図である。
【図３】実施例中にあるゼオライト３（モルデナイト）のＸ線回折図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a catalyst that selectively oxidizes carbon monoxide, and in particular, reforming for removing carbon monoxide contained in a reformed gas used as a hydrogen supply source in a polymer electrolyte fuel cell. The present invention relates to a gas oxidation catalyst.
[0002]
[Prior art]
Conventionally, a polymer electrolyte fuel cell (hereinafter referred to as “PEFC”) using a platinum-based electrode catalyst has widely used hydrogen gas obtained by reforming a gas such as methane as its fuel. Yes. Such a reformed gas is used in consideration of cost.
[0003]
However, the reformed gas contains carbon monoxide which is inevitably generated during the reforming. Although the carbon monoxide content itself is a small amount of about 1%, this small amount of carbon monoxide acts as a catalyst poison for the platinum-based electrode catalyst, and is serious due to the poisoning of the PEFC platinum-based electrode catalyst. It was known to cause performance degradation.
[0004]
In order to solve this problem, it has been required to reduce the amount of such carbon monoxide in the reformed gas to 1/100 or less. In order to satisfy this requirement, about 2% oxygen gas is mixed with the reformed gas supplied to the fuel cell, and “a method of previously oxidizing carbon monoxide coexisting with a platinum-supported γ-alumina catalyst into carbon dioxide”. , “Methods of oxidizing carbon monoxide coexisting on the electrode catalyst of a fuel cell to carbon dioxide” have been proposed by Gottsfeld et al.
[0005]
In the method proposed by Gottesfeld et al., When carbon monoxide is oxidized to carbon dioxide, hydrogen gas that should be the fuel is also oxidized and consumed at the same time, resulting in a reduction in fuel utilization efficiency. It was. This is thought to be because catalyst particles supported on carbon black, which is γ-alumina or an electrode catalyst, are exposed on the surface of the carrier, and hydrogen that should be a fuel is simultaneously adsorbed and oxidized together with carbon monoxide. It was. The rate of adsorption is proportional to the gas partial pressure. That is, since hydrogen, which is the main component of the reformed gas, has a high partial pressure, the consumption rate of hydrogen increases.
[0006]
In order to solve such problems, Watanabe is a catalyst that can selectively oxidize carbon monoxide in reformed gas, which is a fuel for fuel cells, and suppress oxidation loss of hydrogen gas, and has a molecular size. A reformed gas oxidation catalyst is proposed in which a catalyst is supported on a carrier having level pores (see Patent Document 1). Among these, it is disclosed that it is preferable to use one or a mixture or alloy of two or more selected from platinum, palladium, rhodium, iridium, ruthenium, nickel, cobalt or iron as a catalyst. Further, JP-A-11-347414 discloses a catalyst in which a platinum alloy catalyst is supported on a zeolitic support, and mordenite is used as the support, and the alloy metal other than platinum in the supported platinum alloy is 20 to 50 atomic%. A reformed gas oxidation catalyst for selectively oxidizing carbon monoxide in the reformed gas is disclosed.
[0007]
The PEFC that uses the reformed gas described above as a fuel can greatly contribute to the practical use of an electric vehicle that will become the mainstream of ZEV (Zero Emission Vehicle) that does not emit harmful substances such as nitrogen oxides at all. is there. Compared to conventional electric vehicles using lead-acid batteries, the travel distance can be dramatically increased. In addition, even if electric vehicles using nickel-hydrogen storage batteries that have solved this mileage problem to some extent have spread, enormous charging power is required, and ultimately carbon dioxide and nitrogen oxide emissions from thermal power generation It may also mean that the total environmental consideration is not sufficient.
[0008]
On the other hand, PEFC that can reduce carbon dioxide emissions with high power generation efficiency uses methanol or the like as a fuel starting material, and uses this as fuel (reformed gas) instead of hydrogen. Obtaining hydrogen from this methanol is not difficult with the current technology, and can be performed by a device that can be mounted on a vehicle. By applying this technology to an electric vehicle, it is possible to provide an electric vehicle that can be used for diversion of existing gas station equipment and that can travel long distances.
[0009]
In consideration of using PEFC in an electric vehicle, it is required that the battery performance does not vary due to a change in the flow rate of hydrogen gas as a fuel. If the hydrogen gas flow rate at the time of acceleration and deceleration of the electric vehicle is changed, if the carbon monoxide in the reformed gas is not sufficiently removed, the running performance of the electric vehicle will be adversely affected. It will be.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-256112 [Patent Document 2]
Japanese Patent Laid-Open No. 11-347414
[Problems to be solved by the invention]
In order not to fluctuate the performance of PEFC, it is necessary to oxidize carbon monoxide in the reformed gas as a fuel to eliminate poisoning by carbon monoxide. Zeolite, particularly mordenite, as a catalyst carrier having the potential to solve this problem, and one or a mixture of two or more selected from platinum, palladium, rhodium, iridium, ruthenium, nickel, cobalt, or iron as catalyst elements, or Although it has been known that the alloy is used as a catalyst for selective oxidation of carbon monoxide, it has been unclear what mordenite has excellent performance.
[0012]
In particular, the catalytic performance required for this reformed gas oxidation catalyst is completely different from that of a general catalyst and is intended for selective oxidation of carbon monoxide. The structure or nature of the is very important. Conventionally, only the structure of the support zeolite has attracted attention, and the influence of the zeolite form has not been known.
[0013]
In addition, the conventionally known catalyst for selective oxidation of carbon monoxide using zeolite as a carrier shows good performance at a low carbon monoxide concentration, but at a concentration of carbon monoxide exceeding 1% or carbon dioxide. In the presence of carbon, satisfactory results were not obtained for both activity and selectivity.
[0014]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, it has been found that the selectivity and activity when selectively oxidizing carbon monoxide in hydrogen are improved by using zeolite with small crystals as a carrier. It came to.
[0015]
The reason is not clear, but since the oxidation reaction is mainly performed in the pores of the zeolite, it is considered that the better the diffusion of the reaction molecules, the more efficiently and selectively the catalytic reaction can proceed. That is, if it takes time for carbon monoxide to enter the pores and become carbon dioxide, the next carbon monoxide cannot enter the pores. In such a case, it is considered that hydrogen having a small molecular diameter easily enters the pores and lowers the selectivity.
[0016]
The present invention has the following configuration. That is, “a catalyst for selective oxidation of carbon monoxide characterized by containing a mordenite-type zeolite having a crystallite diameter of 120 nm or less determined by a powder X-ray diffraction method and a metal having oxidation ability.” A method for oxidizing carbon monoxide, comprising contacting a gas containing carbon oxide with oxygen. "
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
[0018]
The first invention in the present invention is “a catalyst for selective oxidation of carbon monoxide characterized by containing a mordenite-type zeolite having a crystallite diameter of 120 nm or less determined by a powder X-ray diffraction method and a metal having oxidation ability” . "
[0019]
The type of zeolite in the present invention is not particularly limited, but a zeolite having pores larger than the carbon monoxide molecular size (0.376 nm) is preferable. Examples thereof include MFI type zeolite, FAU type zeolite, β type zeolite, mordenite type zeolite, MEL type zeolite, MTW type zeolite, MWW type zeolite and the like. Of these, zeolite with a mordenite structure is most preferable from the viewpoint of selective oxidation. However, as long as the zeolite has pores larger than the molecular diameter of carbon monoxide, carbon monoxide is selectively adsorbed over hydrogen, so the effect of small crystallites appears in any structure zeolite. . The zeolite may be not only a crystalline aluminosilicate but also a metallosilicate such as crystalline iron silicate containing a metal other than aluminum.
[0020]
The crystallite diameter of the zeolite in the present invention is essential to be 120 nm or less, and this can be determined by a powder X-ray diffraction method. Hereinafter, taking mordenite as an example, how to find it will be described.
[0021]
The simplest method for examining whether zeolite has a mordenite structure is powder X-ray diffraction. When powder X-ray diffraction is performed, it can be determined by whether there is a peak at the same position as known mordenite. As measurement conditions, for example, tube (X-ray source) = CuKα ray (λ = 0.15418 nm), tube voltage = 34 kV, tube current = 40 mA, wide-angle goniometer, sampling width = 0.020 degrees, scan speed 2 Degree / minute divergence slit = 1 degree, light receiving slit = 0.15 mm.
[0022]
In the present invention, it is essential that the crystallite diameter is 120 nm or less. The size of the crystallite can be easily examined by powder X-ray diffraction. The crystallite diameter of the present invention is measured by the following method. (200) The crystallite diameter is calculated by substituting the half-value width obtained from the peak of the crystal plane into the Sierra equation (I). (200
) The crystal plane peak is a peak with a lattice spacing d = 0.90 ± 0.02 nm, the peak intensity is large, and there is almost no overlap with other peaks. Is calculated.
[0023]
Crystallite diameter = K × λ / (β ₁ × cos θ) (I)
(Where, K: constant (0.9), lambda: X-ray wavelength of (0.15418nm), θ: 1/ 2 of the diffraction angle, beta _1: device correcting was performed (200) crystal plane at half the Price range (rad).)
[0024]
Further, the half width correction β ₁ in the equation (I) is performed using the following equations (II) and (III).
β ₂ ² = βm ² -βo ² (II)
β ₁ = β ₂ × π / 180 (III)
(Where βm: actual value (degree) of half-value width of (200) crystal plane peak, βo: actual value (degree) of half-value width of (111) crystal plane of Si, which is a standard material)
The mordenite used in the catalyst of the present invention has a crystallite size determined by this method of 120 nm or less, more preferably 100 nm or less.
[0025]
In addition, the crystallite size can be similarly determined for zeolites other than mordenite.
[0026]
In the present invention, it is essential to include a metal having an oxidizing ability. These metals are not particularly limited as long as they have an oxidizing ability. For example, platinum, palladium, rhodium, iridium, ruthenium, nickel, cobalt, copper, vanadium, manganese, molybdenum, silver, rhenium, gold, osmium or iron One kind or a mixture or alloy of two or more kinds selected from the above. More preferred is one or a mixture or alloy selected from platinum, palladium, ruthenium, copper and iron, and particularly preferred is a metal containing platinum and / or palladium.
[0027]
The method of introducing the metal is not particularly limited, but an equilibrium adsorption method or an ion exchange method is preferable. Among these, the ion exchange method is the most preferable method.
[0028]
The method of ion exchange is not particularly limited, and a generally known method may be used. In addition, the order of removing (burning off) organic substances mixed during zeolite synthesis, which will be described later, and ion exchange may be performed first, but the catalyst is more highly dispersed to support an expensive catalyst such as platinum. For the purpose of reducing the amount, it is preferable to perform the ion exchange treatment first.
[0029]
In the present invention, it is important to use a zeolite having a small crystallite, and it is essential that the crystallite diameter measured by the powder X-ray diffraction method is 120 nm or less. It can also be observed and measured with an electron microscope (SEM). When the size of a single crystal is examined with a scanning electron microscope (SEM), a crystallite is defined as a particle (primary particle) that is recognized as a minimum unit particle when measured at a magnification of 10,000 times. The preferred crystallite size in the present invention is that the length of the major axis is 0.24 μm or less, more preferably the length of the major axis is 0.20 μm or less.
[0030]
In the present invention, Ru essential der to be small zeolite crystallite. Therefore, it is necessary to make microcrystalline zeolite by a special method. For example, mordenite includes natural products and synthetic products, but synthetic products are preferred in the present invention. Various methods have been disclosed so far for the synthesis of mordenite. For example, JP-B-47-46677, JP-A-55-126529, JP-A-58-91032 and the like can be mentioned. The size of the mordenite crystallites varies depending on the composition of the reaction mixture at the time of synthesis, crystallization temperature, crystallization time, stirring speed, etc. When a nitrogen-containing basic organic compound such as hydroxide or a surfactant such as polyethylene glycol is present, the crystallite tends to be small. As for the composition ratio in the reaction mixture, the crystallite size varies in a complicated manner depending on the concentration of silica and alumina and the concentration of alkali, so it is necessary to select an optimum composition ratio as appropriate. Under crystallization conditions, crystallites tend to be smaller when the crystallization temperature is lowered, the crystallization time is shortened, or the stirring speed is increased.
[0031]
When a nitrogen-containing basic organic compound such as tetraethylammonium hydroxide or a surfactant such as polyethylene glycol is present in the reaction mixture during zeolite synthesis, these nitrogen-containing basic organic compounds and Surfactants may be incorporated. However, it is considered that these nitrogen-containing basic organic compounds and the like block the zeolite pores and inhibit the contact between the catalytic active site and carbon monoxide, and therefore it is preferable to burn them off at 500 ° C. or higher before use.
[0032]
The method of burning off may be pre-baked in a zeolite state, may be fired after preparing the catalyst, or may be fired by contacting with oxygen in the reaction tube immediately before the reaction.
[0033]
Furthermore, the present invention is “a method for oxidizing carbon monoxide, characterized by contacting a catalyst, a gas containing carbon monoxide, and oxygen”. As a carbon monoxide oxidation reaction system, any of a fixed bed, a moving bed, and a fluidized bed can be used, but a fixed bed flow system is particularly preferable in terms of ease of operation. In particular, in the case of an automobile catalyst, it is preferable from the viewpoint that pressure loss is small to use a method in which the surface of the honeycomb-shaped support is coated with zeolite microcrystals as a catalyst and the reaction gas is fed into the pores of the honeycomb. In this case, it is preferable that the zeolite crystallite is small because coating is easy and the strength of the coating becomes high. Further, since the outer surface area of the catalyst is increased, there is an advantage that the honeycomb area may be small, and the catalyst of the present invention is particularly effective when coated on the honeycomb-shaped support.
[0034]
The reaction temperature is preferably 20 to 250 ° C, more preferably 20 to 150 ° C.
[0035]
The present invention may be either a gas phase reaction or a liquid phase reaction, but a gas phase reaction is preferred.
[0036]
The composition of the reaction gas must contain carbon monoxide and oxygen, but it may contain other gases contained in the atmosphere such as hydrogen, nitrogen, carbon dioxide, and argon. I do not care. The carbon monoxide selective oxidation catalysts known so far are not well known for their performance in the situation where carbon dioxide coexists, but the catalyst of the present invention exhibits high activity even when carbon dioxide coexists. Show.
[0037]
The reaction time in the present invention, as the space velocity (WHSV = weight hourly space velocity per time), 0.01~30h ^-1, preferably in the range of 0.05~5h ^-1.
[0038]
Moreover, it is preferable to activate a catalyst by making a catalyst contact hydrogen at high temperature immediately before performing reaction in this invention. The contact temperature is preferably 200 ° C. or higher, more preferably 300 ° C. or higher, and more preferably 500 ° C. or higher.
[0039]
【Example】
Hereinafter, the present invention will be described with examples, but the present invention is not limited thereto.
[0040]
(Zeolite synthesis)
Zeolite 1
Solid caustic soda (NaOH content 96.0 wt%, H ₂ O content 4.0 wt%, Katayama Chemical) 1.28 grams, sodium aluminate solution (Al ₂ O ₃ content 18.5 wt%, NaOH content 26.1 wt%, H ₂ O content 55.4Wt%, Sumitomo chemical) 9.38 g, trimethylbenzylammonium hydroxide (hereinafter "TMBAOH" and designation) (TMBAOH content 10 wt%, H ₂ O content of 90 wt%, Tokyo Kasei) 54.86 g A uniform solution was added to 186.07 grams of distilled water. The mixture in hydrated silicic acid (SiO2 content 91.6wt%, Al ₂ O ₃ content 0.33 wt%, NaOH content of 0.27 wt%, Nipseal VN-3, Japan Silica) 29.53 g slowly with stirring In addition, a uniform slurry aqueous reaction mixture was prepared. The composition ratio (molar ratio) of this reaction mixture was as follows.
[0041]
SiO ₂ / Al ₂ O ₃ = 25
OH / SiO ₂ = 0.3
Q / (Q + Na) = 0.305 (where Q is TMBAOH)
H ₂ O / SiO ₂ = 30
The reaction mixture was sealed in a 400 ml autoclave and then reacted at 160 ° C. for 10 days with stirring at 250 rpm.
[0042]
After completion of the reaction, washing with distilled water 5 times and filtration were repeated, followed by drying at about 120 ° C. overnight. When the obtained product was subjected to X-ray diffraction, an X-ray diffraction pattern as shown in FIG. 1 was shown, and it was found to be mordenite. The X-ray diffraction conditions were such that the X-ray source was Cu / 34 kV / 40 mA and the scan speed was 2 degrees / minute. The crystallite diameter calculated based on the half-value width obtained from the peak of the (200) crystal plane was 45 nm. When elemental analysis of the crystal was measured by fluorescent X-ray, the mordenite had a silica / alumina molar ratio of 19.5.
[0043]
Zeolite 2
Solid caustic soda (NaOH content 96.0 wt%, H ₂ O content 4.0 wt%, Katayama Chemical) 1.28 grams, sodium aluminate solution (Al ₂ O ₃ content 18.5 wt%, NaOH content 26.1 wt%, H ₂ O content 55.4Wt%, Sumitomo chemical) 9.38 g, triethyl methyl ammonium hydroxide (hereinafter "TEMAOH" and designation) (TEMAOH content 20 wt%, H ₂ O content of 80 wt%, Tokyo Kasei) 27.43 g A uniform solution was added to 213.50 grams of distilled water. The mixture in hydrated silicic acid (SiO2 content 91.6wt%, Al ₂ O ₃ content 0.33 wt%, NaOH content of 0.27 wt%, Nipseal VN-3, Japan Silica) 29.53 g slowly with stirring In addition, a uniform slurry aqueous reaction mixture was prepared. The composition ratio (molar ratio) of this reaction mixture was as follows.
[0044]
SiO ₂ / Al ₂ O ₃ = 25
OH / SiO ₂ = 0.3
Q / (Q + Na) = 0.305 (where Q is TEMAOH)
H ₂ O / SiO ₂ = 30
The reaction mixture was sealed in a 400 ml autoclave and then reacted at 160 ° C. for 10 days with stirring at 250 rpm.
[0045]
After completion of the reaction, washing with distilled water 5 times and filtration were repeated, followed by drying at about 120 ° C. overnight. When the obtained product was subjected to X-ray diffraction, an X-ray diffraction pattern as shown in FIG. 2 was shown, and it was found to be mordenite. The X-ray diffraction conditions were such that the X-ray source was Cu / 34 kV / 40 mA and the scan speed was 2 degrees / minute. The crystallite diameter calculated based on the half width obtained from the peak of the (200) crystal plane was 55 nm. When elemental analysis of the crystal was measured by fluorescent X-ray, the mordenite had a silica / alumina molar ratio of 19.1.
[0046]
Zeolite 3
Solid caustic soda (NaOH content 96.0 wt%, H ₂ O content 4.0 wt%, Katayama Chemical) 0.40 grams, sodium aluminate solution (Al ₂ O ₃ content 18.5 wt%, NaOH content 26.1 wt%, H ₂ O content 55.4Wt%, Sumitomo chemical) 23.89 g tetraethyl ammonium hydroxide (hereinafter "TEAOH" and designation) (TEAOH content 20 wt%, H ₂ O content of 80 wt%, Sanyo Kasei) 55.2 g distilled A homogeneous solution was added to 567 grams of water. The mixture in hydrated silicic acid (SiO2 content 91.6wt%, Al ₂ O ₃ content 0.33 wt%, NaOH content of 0.27 wt%, Nipseal VN-3, Japan Silica) 65.5 g slowly with stirring In addition, a uniform slurry aqueous reaction mixture was prepared. The composition ratio (molar ratio) of this reaction mixture was as follows.
[0047]
SiO ₂ / Al ₂ O ₃ = 22
OH / SiO ₂ = 0.245
Q / (Q + Na) = 0.305 (where Q is TEAOH)
H ₂ O / SiO ₂ = 35
The reaction mixture was sealed in a 1000 ml autoclave and then reacted at 160 ° C. for 7 days with stirring at 250 rpm.
[0048]
After completion of the reaction, washing with distilled water 5 times and filtration were repeated, followed by drying at about 120 ° C. overnight.
[0049]
When the obtained product was subjected to X-ray diffraction, an X-ray diffraction pattern as shown in FIG. 3 was obtained, and it was found to be mordenite. The X-ray diffraction conditions were such that the X-ray source was Cu / 34 kV / 40 mA and the scan speed was 2 degrees / minute. Further, the crystallite diameter calculated based on the half width obtained from the peak of the (200) crystal plane was 100 nm. When elemental analysis of the crystal was measured by fluorescent X-ray, the mordenite had a silica / alumina molar ratio of 18.5. As a result of observing the zeolite particles with a field emission scanning electron microscope (FE-SEM), the major axis of the crystallite was 0.12 μm.
[0050]
(Catalyst adjustment)
Catalyst 1
1 g of zeolite 1 was immersed in 2 g of a 5 wt% tetraamminedichloroplatinum monohydrate (manufactured by Mitsuwa Chemicals) aqueous solution at 80 ° C. for 30 minutes. Thereafter, washing with distilled water twice and filtration were repeated, followed by drying at 80 ° C. overnight.
[0051]
The obtained powder was tableted and then crushed and sized to a particle size of 250 to 425 μm.
[0052]
Catalyst 2
Instead of zeolite 1, zeolite 2 was used, and catalyst 2 was prepared in the same manner as catalyst 1.
[0053]
Catalyst 3
Instead of zeolite 1, zeolite 3 was used, and catalyst 3 was prepared in the same manner as catalyst 1.
[0054]
Catalyst 4
In place of zeolite 1, Tosoh zeolite (Mordenite HSZ-642NAA, Lot. 6BAA9Y01) was used, and catalyst 4 was prepared in the same manner as catalyst 1. X-ray diffraction measurement was performed, and the crystallite diameter calculated based on the half width obtained from the peak of the (200) crystal plane was 150 nm. When elemental analysis of the crystal was measured by fluorescent X-ray, the mordenite had a silica / alumina molar ratio of 19.5. As a result of observing the zeolite particles with a field emission scanning electron microscope (FE-SEM), the major axis of the crystallite was 0.26 μm.
[0055]
Catalyst 5
1 g of zeolite 3 calcined at 550 ° C. for 3 hours at a rate of temperature increase of 1 ° C./minute was immersed in 2 g of an aqueous solution of 5 wt% tetraamminedichloroplatinum monohydrate (manufactured by Mitsuwa Chemicals) for 30 minutes at 80 ° C. Thereafter, washing with distilled water twice and filtration were repeated, followed by drying at 80 ° C. overnight.
[0056]
The obtained powder was tableted and then crushed and sized to a particle size of 250 to 425 μm.
[0057]
Catalyst 6
1 g of zeolite 3 at 80 ° C. for 30 minutes, 0.6 g of 5 wt% tetraamminedichloroplatinum monohydrate (manufactured by Mitsuwa Chemicals) aqueous solution, 0.2 g of 5 wt% aqueous ferric nitrate (manufactured by Nacalai Tesque) and water 1 Soaked in 2 g of mixture. Thereafter, washing with distilled water twice and filtration were repeated, followed by drying at 80 ° C. overnight.
[0058]
The obtained powder was tableted and then crushed and sized to a particle size of 250 to 425 μm.
[0059]
Example 1
Take the catalyst 1 in a 0.2 g reaction tube, raise the temperature to 500 ° C. while flowing air at 20 ml / min, hold it for 30 minutes, then flow nitrogen at 30 ml / min for 5 minutes, and continue to add 30 ml of hydrogen at a temperature of 500 ° C. Flowed at / min for 30 minutes. Thereafter, the temperature of the reaction tube was raised to 200 ° C. while flowing hydrogen at 30 ml / min, and then the reformed gas (hydrogen gas containing 1.6% oxygen, 2.8% carbon monoxide, 6.0% nitrogen and 22.3% carbon dioxide) was added to 27 ml / The oxygen content, carbon monoxide content, and nitrogen content at the outlet side of the reaction tube were detected by gas chromatography, and the oxygen conversion rate, carbon monoxide conversion rate, and carbon monoxide selectivity were determined. The results are shown in Table 1.
[0060]
Example 2
In Example 1, the reaction was performed under the same conditions as in Example 1 except that catalyst 2 was used instead of catalyst 1. Table 1 shows the obtained oxygen conversion rate, carbon monoxide conversion rate, and carbon monoxide selectivity.
[0061]
Example 3
In Example 1, the reaction was performed under the same conditions as in Example 1 except that catalyst 3 was used instead of catalyst 1. Table 1 shows the obtained oxygen conversion rate, carbon monoxide conversion rate, and carbon monoxide selectivity.
[0062]
Comparative Example 1
In Example 1, the reaction was performed under the same conditions as in Example 1 except that catalyst 4 was used instead of catalyst 1. Table 1 shows the obtained oxygen conversion rate, carbon monoxide conversion rate, and carbon monoxide selectivity.
[0063]
Example 4
In Example 1, the reaction was performed under the same conditions as in Example 1 except that the catalyst 5 was used instead of the catalyst 1. Table 1 shows the obtained oxygen conversion rate, carbon monoxide conversion rate, and carbon monoxide selectivity.
[0064]
Example 5
In Example 1, the reaction was performed under the same conditions as in Example 1 except that catalyst 6 was used instead of catalyst 1. Table 1 shows the obtained oxygen conversion rate, carbon monoxide conversion rate, and carbon monoxide selectivity.
[0065]
[Table 1]

[0066]
The oxygen conversion rate shown in this table is an index indicating how many percent of oxygen molecules in the reformed gas are consumed, and the CO conversion rate is one of the reformed gas. This is an index showing how many carbon monoxide molecules of the carbon oxide molecules are consumed.
[0067]
【The invention's effect】
In the method of selectively oxidizing carbon monoxide, the catalytic activity could be greatly improved by using a catalyst having a small crystallite. Moreover, even if the carbon monoxide concentration contained in the reformed gas component exceeds 1%, or even in the presence of carbon dioxide concentration, a highly active catalyst for selective oxidation of carbon monoxide could be obtained.
[Brief description of the drawings]
FIG. 1 is an X-ray diffraction pattern of zeolite 1 (mordenite) in Examples.
FIG. 2 is an X-ray diffraction pattern of zeolite 2 (mordenite) in Examples.
FIG. 3 is an X-ray diffraction pattern of zeolite 3 (mordenite) in Examples.

Claims (3)

A catalyst for selective oxidation of carbon monoxide, comprising a mordenite-type zeolite having a crystallite size of 120 nm or less determined by a powder X-ray diffraction method and a metal having oxidation ability. The catalyst for selective oxidation of carbon monoxide according to claim 1, wherein the metal having oxidation ability is at least one selected from platinum, ruthenium, and iron . A method for oxidizing carbon monoxide, comprising contacting the catalyst for selective oxidation of carbon monoxide according to claim 1 or 2 with a gas containing carbon monoxide and oxygen.

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