JP2001220109A - Method of reducing carbon monoxide in hydrogen- containing gas and catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a catalyst for efficiently reducing the concentration of carbon monoxide in a hydrogen-containing gas obtained by a methanol reforming reaction. SOLUTION: Carbon monoxide in the hydrogen-containing gas and oxygen are brought into contact with each other in the presence of a cobalt-platinum coexistence based catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a catalyst for reducing carbon monoxide in a hydrogen-containing gas using a catalyst.
The present invention relates to a method and a catalyst for reducing carbon monoxide in a hydrogen-containing gas produced by a reforming reaction of a hydrocarbon or methanol.

[0002]

2. Description of the Related Art Hydrogen-containing gas is produced by reforming hydrocarbons, methanol and the like with steam, and is used as a raw material for organic chemicals. ing. These hydrogen-containing gases contain carbon monoxide, and when used as a hydrogen source for a fuel cell, the carbon monoxide is adsorbed on the platinum catalyst of the electrode of the fuel cell and deteriorates its function as a catalyst. It is necessary to lower the hydrogen concentration as much as possible. The allowable concentration of carbon monoxide is, for example, several percent or less in the case of a phosphoric acid fuel cell, and several tens ppm or less in the case of a polymer electrolyte battery. Methanol can perform a reforming reaction with steam at a relatively low temperature, and has a low content of carbon monoxide, so that it can be advantageously used as a hydrogen source for a fuel cell.
For this reason, development of a fuel cell using methanol as a raw material, particularly development of a fuel cell for a vehicle that can be mounted on a vehicle, is being promoted.

A method of reducing carbon monoxide concentration by oxidizing carbon monoxide in a hydrogen-containing gas to carbon dioxide using a catalyst is disclosed in Japanese Patent Application Laid-Open No. 5-245376. A method of performing conversion of carbon monoxide by steam using a magnesium catalyst has been described,
JP-A-8-295502 describes a method for selectively oxidizing and removing carbon monoxide using a catalyst in which ultrafine gold particles are dispersed and supported on a metal oxide. Japanese Patent Application Laid-Open No. 9-30802 discloses an apparatus for reducing the concentration of carbon monoxide in a hydrogen-containing gas obtained by a reforming reaction of methanol using a platinum-ruthenium catalyst. JP-A-11-102719 describes an apparatus for selectively oxidizing the concentration of carbon monoxide contained in a hydrogen-rich gas using a catalyst obtained by adding an alkali metal to ruthenium.

[0004]

The above-mentioned method using a copper oxide / aluminum oxide / magnesium oxide catalyst (JP-A-5-245376) has a high reaction temperature of 300 to 400 ° C. and a high conversion rate of carbon monoxide. small. A method using a catalyst in which ultrafine gold particles are dispersed and supported on a metal oxide (JP-A-8-295502)
Reacts at low temperatures, but the catalyst is very expensive.
Also, a method using a platinum-ruthenium catalyst (Japanese Patent Application Laid-Open No. 9-3080)
No. 2) and a method using a catalyst obtained by adding an alkali metal to ruthenium (JP-A-11-102719) are also expensive,
In addition, part of carbon monoxide easily reacts with hydrogen to cause methanation. Methanation consumes a large amount of hydrogen, generates a large amount of heat during the reaction, easily causes temperature runaway, and makes it difficult to control the reaction temperature.

An object of the present invention is to provide a method and a catalyst for efficiently reducing the concentration of carbon monoxide in a hydrogen-containing gas obtained by a reforming reaction of methanol for the development of a fuel cell. is there.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies on a method for reducing the concentration of carbon monoxide in a hydrogen-containing gas, which has the above-mentioned problems, and as a result, using a catalyst coexisting with cobalt / platinum, The present inventors have found that the concentration of carbon monoxide in a hydrogen-containing gas can be efficiently reduced by bringing carbon and oxygen into contact with each other, and arrived at the present invention.

That is, the present invention provides a method for reducing carbon monoxide in a hydrogen-containing gas, which comprises bringing carbon monoxide and oxygen into contact with each other in the presence of a cobalt-platinum coexisting catalyst. This is a catalyst for reducing carbon monoxide, which is made of a catalyst.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The hydrogen-containing gas as a raw material in the present invention is not particularly limited, but is usually produced by steam reforming or partial oxidation of hydrocarbon or methanol.
As the hydrocarbon, gaseous natural gas containing methane as a main component, liquid LPG, naphtha, light oil and the like are used. A nickel-based catalyst is used in a hydrocarbon steam reforming furnace, and is reacted at 800 to 1000 ° C. to produce a synthesis gas containing hydrogen, carbon monoxide and carbon dioxide as main components. As the hydrogen-containing gas as the raw material in the present invention, a gas obtained by converting carbon monoxide in the synthesis gas produced as described above to carbon dioxide using an iron-based catalyst or a copper-based catalyst is used. The hydrogen-containing gas usually contains about 1 mol% of carbon monoxide.

[0009] Steam reforming of methanol is carried out at 200 to 350 ° C using a copper-zinc catalyst or a noble metal catalyst such as Pd or Pt.
To produce a synthesis gas containing hydrogen and carbon dioxide as main components. Generally, when a noble metal-based catalyst is used, the synthesis gas contains about 1 to 5 mol% of carbon monoxide. When a copper-zinc-based catalyst is used, the synthesis gas contains 1 mol% or less. Although carbon monoxide is included, these synthesis gases are used directly as the raw material hydrogen-containing gas in the present invention.

In the present invention, by adding an oxygen-containing gas to the above-mentioned raw material hydrogen-containing gas and reacting it with a nickel-platinum coexisting catalyst, carbon monoxide is selectively oxidized to carbon dioxide, The carbon monoxide concentration is reduced. As the composition containing cobalt and platinum as the catalytically active components, forms such as a coprecipitation catalyst and a supported catalyst can be selected. As the coprecipitation catalyst, a method of precipitating from an aqueous solution containing cobalt and platinum with, for example, an alkali carbonate precipitant can be used. As the supported catalyst, a platinum-containing component may be supported on a cobalt-containing catalyst obtained by, for example, adding a carrier component slurry to a cobalt precipitation slurry and carbonating with a carbon dioxide gas. As the catalyst carrier, alumina, silica or the like having a high surface area is suitable, but the order and method for carrying the active ingredient are not particularly limited, and known methods such as impregnation method and precipitation method can be used in combination. For use in a vehicle-mounted fuel cell, a catalyst comprising a carrier carrying a cobalt-containing component and a platinum-containing component is preferred. As a composition content, cobalt is
0.1 to 80% by weight, preferably 0.5 to 50% by weight;
Is 0.05 to 50% by weight, preferably 0.2 to 5% by weight.

The reaction conditions for selectively oxidizing carbon monoxide are as follows. The reaction temperature is usually from 40 to 200 ° C, preferably from 60 to 160 ° C. The amount of oxygen added to the hydrogen-containing gas is 0.5 to 4 times the carbon monoxide content, preferably
0.5 to 2 times. The pressure ranges from normal pressure to 20 atm (0.1 to 2 MPa). The amount of the catalyst used is 100 to 50,000 [1 / h], preferably 50 to 30,000 [1 / h] as a gas hourly space velocity (GHSV).

The cobalt-platinum coexisting catalyst used in the method of the present invention is characterized by a high oxygen reaction rate and a remarkably high CO oxidation selectivity at low temperatures. That is, at temperatures up to 260 ° C., the methanation reaction due to the reaction between carbon monoxide and hydrogen hardly occurs. At a temperature below 200 ° C, no reverse shift reaction occurs between carbon dioxide and hydrogen, and the carbon dioxide generation reaction by oxidation of carbon monoxide is performed with a selectivity of 50% or more with respect to oxygen consumption. In the method of the present invention, when treating a hydrogen-containing gas by steam reforming of methanol containing about 1 mol% of CO, the CO concentration can be reduced to 0.1 mol% or less at a relatively low temperature of about 30 to 200 ° C. And the amount of hydrogen combustion is extremely small. Further, the CO concentration can be reduced to 0.01 mol% or less in a temperature range of about 40 ° C. to 180 ° C. Therefore, the hydrogen-containing gas treated in the temperature range of about 30 to 200 ° C. by the method of the present invention is supplied to the phosphoric acid type fuel cell by 40 to 180 ° C.
The hydrogen-containing gas treated in a temperature range of about ° C. can be directly used for a polymer electrolyte battery. Therefore, the hydrogen-containing gas treated by the method of the present invention can be used very suitably for a fuel cell of a vehicle type or the like.

[0013]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples. The raw material gas in the evaluation of the catalyst performance in each of Examples and Comparative Examples contained 0.5 mol% of CO, O ₂
0.5 mol%, CO ₂ 24 mol%, H ₂ 75 mol% (O ₂ / C
An oxygen-containing reformed gas having a composition (O molar ratio = 1.0) was used.
Under normal pressure, at a constant space velocity (SV), increase the reaction temperature to 40-260.
The gas composition after the reaction when the temperature was changed to ° C. was analyzed by gas chromatography. In the graph showing the results of the evaluation of the catalyst performance, the oxygen reaction rate indicates the reaction rate (conversion rate) of oxygen in the raw material gas, and the CO oxidation selectivity indicates the ratio of reaction oxygen that contributed to the CO oxidation reaction. . CO in reaction oxygen
Those that did not contribute to the oxidation reaction are mostly consumed in the combustion of hydrogen.

Example 1 Using an aqueous solution in which 0.5% by weight of cobalt acetate dihydrate was dissolved as Co, commercially available alumina spheres (average diameter 1.5 mm, BET specific surface area: 200 to 240 m ³ / g) were applied to an evaporator. Then, 0.5 wt% of Co was supported by drying under reduced pressure and dried. Next, 0.5wt% Pt
Using a corresponding acetone solution of acetylacetonato platinum,
Further, 0.5 wt% of platinum was supported by drying under reduced pressure by an evaporator, dried, and calcined at 360 ° C. to obtain 0.5 wt% Co-0.5 wt% Pt /
An alumina catalyst was obtained. Catalyst performance evaluation (SV = 13000 [1 / h])
FIG. 1 shows the results. When using this catalyst, 40-260 ° C
Methane was not generated in the temperature range of
The CO concentration falls to 0.05 mol% or less in the range of -190 ° C. The oxygen reaction rate in this temperature range is 90% or more, and C
O oxidation selectivity is about 50%.

Comparative Example 1 In Example 1, a 0.5 wt% Co / alumina catalyst was obtained without carrying platinum. The reaction was carried out under the same conditions as in Example 1 (SV
= 13000 [1 / h]). The results are shown in FIG. In the catalyst, 40-
No methane is generated in the temperature range of 260 ° C, but about 230 ° C
Otherwise, the oxygen reaction rate cannot be increased to 80% or more, the CO oxidation selectivity is 40% or less, and the CO concentration becomes 0.4% or less.
mol% or less could not be achieved.

Comparative Example 2 A 1.0 wt% Pt / alumina catalyst was obtained in Example 1 without supporting cobalt. The reaction was carried out under the same conditions as in Example 1.
(SV = 13000 [1 / h]). The results are shown in FIG. If the temperature of the catalyst is not higher than about 170 ° C., the oxygen reaction rate cannot be increased to 80% or more, the CO oxidation selectivity is 55% or less, and the
CO concentration is below 0.1mol% in the temperature range of ~ 220 ℃,
The CO concentration could not be reduced to 0.03 mol% or less.

Comparative Example 3 In Example 1, 1.0 wt% Ru / alumina catalyst was obtained by using acetylacetonatoruthenium instead of acetylacetonatoplatinum without carrying cobalt. The reaction was carried out under the same conditions as in Example 1 (SV = 13000 [1 / h]). FIG. 4 shows the results. In the catalyst, methane is generated at 150 ° C. or higher, and the amount of methane generated increases rapidly with an increase in temperature. About 100 ℃
Otherwise, the oxygen reaction rate cannot be increased to 80% or more, the CO oxidation selectivity is 50% or less, and the CO concentration becomes 0.05 mol% or less at a temperature of about 190 ° C or more. Therefore, the catalyst cannot effectively use oxygen to reduce the CO concentration, and consumes a large amount of hydrogen for combustion of methane and hydrogen at high temperatures.

[0018]

As is clear from the above embodiments, according to the method of the present invention, the hydrogen-containing gas obtained by steam reforming of methanol containing about 1% of CO can be used at a relatively low temperature of about 30 to 200 ° C. CO concentration can be 0.1 mol% or less,
Very low hydrogen loss. Therefore, the hydrogen-containing gas treated by the method of the present invention can be very suitably used for a fuel cell of a vehicle type or the like, and the present invention has great industrial significance.

[Brief description of the drawings]

FIG. 1 is a drawing showing the results of performance evaluation of a catalyst of Example 1.

FIG. 2 is a drawing showing the results of performance evaluation of a catalyst of Comparative Example 1.

FIG. 3 is a drawing showing the results of performance evaluation of a catalyst of Comparative Example 2.

FIG. 4 is a drawing showing the results of performance evaluation of a catalyst of Comparative Example 3.

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[Procedure amendment]

[Submission date] April 27, 2000 (200.4.2
7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

That is, the present invention provides a method for reducing carbon monoxide in a hydrogen-containing gas, which comprises bringing carbon monoxide and oxygen into contact with each other in the presence of a cobalt-platinum coexisting catalyst, and a method for reducing a component containing cobalt and platinum on a carrier. This is a catalyst for reducing carbon monoxide, which is made of a catalyst.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

Example 1 An aqueous solution in which 0.5% by weight of cobalt acetate dihydrate was dissolved as Co was used to evaporate commercially available alumina spheres (average diameter 1.5 mm, BET specific surface area: 200 to 240 m ² / g). Was dried under reduced pressure to carry 0.5 wt% of Co and dried. Next, using an acetone solution of acetylacetonatoplatinum equivalent to 0.5 wt% Pt, 0.5% by weight of platinum was further supported by drying under reduced pressure with an evaporator,
After drying, it was calcined at 360 ° C. to obtain 0.5 wt% Co-0.5 wt% Pt / alumina catalyst. FIG. 1 shows the results of the catalyst performance evaluation (SV = 13000 [1 / h]). When the catalyst is used, methane is not generated in the temperature range of 40 to 260 ° C, and the reaction temperature is about 40 to 190 ° C.
The CO concentration falls to 0.05 mol% or less in the range of ° C.
The oxygen reaction rate in this temperature range is 90% or more, and the CO oxidation selectivity is about 50%.

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Claims (3)

[Claims] 1. A method for reducing carbon monoxide in a hydrogen-containing gas, which comprises contacting carbon monoxide with oxygen in the presence of a cobalt-platinum coexisting catalyst. 2. The method for reducing carbon monoxide in a hydrogen-containing gas according to claim 1, wherein 0.5 to 2 times the amount of oxygen contained in the hydrogen-containing gas is contacted at 30 to 200 ° C. 3. A catalyst for reducing carbon monoxide comprising a carrier carrying cobalt and platinum-containing components.