JPH08295502A - Method for removing carbon monoxide in hydrogen-containing gas with gold catalyst - Google Patents

Abstract

PURPOSE: To selectively remove only carbon monoxide by treating a gas contg. hydrogen and carbon monoxide with a gold catalyst. CONSTITUTION: This gold catalyst is prepared by dispersedly depositing a gold superfine particle on a metal oxide. The metal oxide is at least one kind among manganese oxide, copper oxide, thin oxide, nicle oxide and their multiple oxide. A gold superfine particle of nm size should be firmly bonded onto a carrier metal oxide in this gold-metal oxide catalyst. The catalyst is appropriately produced by precipitation, coprecipitation, etc. Normally, the diameter of the primary particle is preferably controlled relatively small to a level of 10-200nm, the relatively large specific surface to >=5m<2> /g and the atomic ratio of gold to metal to 1/1250 to 1/9. The reaction condition is not specifically limited, however the temp. is preferably controlled to 30-200 deg.C and the pressure to 1-10atm. Although the amt. of catalyst to be used is not specifically restricted, the space velocity is practically controlled to 1000-50,000hr<-1> .ml/g.catalyst.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a gas containing hydrogen and carbon monoxide, which is obtained by, for example, air reforming or steam reforming of hydrocarbons such as methane and methanol.
The present invention relates to a method for producing a hydrogen-containing gas or hydrogen gas containing no carbon monoxide by selectively oxidizing carbon monoxide in the presence of a gold catalyst.

[0002]

2. Description of the Related Art Gas produced by air reforming or steam reforming hydrocarbons such as methanol and methane contains hydrogen as a main component, but is accompanied by C.
Often it is necessary to remove O 2. For example, steam reforming of methanol carried out at a temperature of about 200 to 250 ° C. in the presence of a copper-based catalyst is represented by the following reaction formula,
It is unavoidable under the present circumstances that carbon monoxide (CO) is mixed in the produced gas at about 1% by volume.

CH ₃ OH + H ₂ O → CO ₂ + 3H ₂ (1) When this methanol reformed gas is used in a solid polymer electrolyte fuel cell, which is expected to be applied as a power source for electric vehicles and the like, The operating temperature of the fuel cell is 100 ℃
Since it is below, the platinum-based metal-supported electrode catalyst is poisoned by CO, and there is a problem that the power generation performance is significantly reduced.

The conventional techniques for selectively removing carbon monoxide in hydrogen using a catalyst have the following problems, respectively. When using platinum-based precious metals (M. Watanabe et al., Chem. Lett. 1995, 21-22, Se H.
Oh et al., J. Catal. 142 , 254-262 (1993)], usually 15
Since a reaction temperature of 0 ° C. or higher is required and the oxidation of hydrogen proceeds much faster, a large amount of hydrogen must be wasted if the CO oxidation removal rate is increased.
This is an essential problem due to the catalytic properties of platinum-based metals that hydrogen oxidation occurs much more easily than carbon monoxide oxidation, and its solution is extremely difficult.

On the other hand, on manganese oxide, copper oxide or a mixed oxide thereof, [SK Chatterjee et al., Indian
J. Technol. 15 , 403-407 (1977)], carbon monoxide oxidation may occur at lower temperatures than hydrogen oxidation, but these oxide catalysts are deactivated by the presence of moisture [CS Brooks, J. .
Catal. 8 , 272 (1967)], so it is not practical.

As described above, the known method of oxidizing and removing carbon monoxide in hydrogen gas by using the platinum-based noble metal catalyst or base metal oxide catalyst is the selectivity for the carbon monoxide to be removed by oxidation and the durability to moisture. In terms of properties, satisfactory results were not obtained, and none of them was suitable for practical use.

[0007]

Therefore, the present invention removes carbon monoxide from a gas containing hydrogen and carbon monoxide obtained by air reforming or steam reforming of hydrocarbons such as methane and methanol. By doing
It is a main object to provide a technique capable of selectively oxidizing and removing carbon monoxide when obtaining a hydrogen-containing gas or hydrogen gas that does not contain carbon monoxide.

[0008]

[Means for Solving the Problem] The present inventors have conducted extensive studies in view of the above problems, and as a result, as a result of using a catalyst in which ultrafine gold particles are dispersed and supported on a specific metal oxide, It has been found that this problem can be substantially solved when carrying out the oxidation reaction of.

That is, the present invention provides the following methods and catalysts: A method for selectively oxidizing and removing carbon monoxide from a gas containing hydrogen and carbon monoxide in the presence of a gold catalyst.

[0010] 2. 2. The method according to item 1, wherein the gold catalyst is a catalyst in which ultrafine gold particles are dispersed and supported on a metal oxide.

3. Item 3. The method according to Item 1 or 2, wherein the metal oxide is at least one of manganese oxide, copper oxide, zinc oxide, tin oxide, titanium oxide, nickel oxide and a composite oxide of these metals.

4. A catalyst for removing carbon monoxide from a gas containing hydrogen and carbon monoxide, characterized in that ultrafine gold particles are dispersed and supported on a metal oxide.

A major feature of the present invention is the use of a gold-metal oxide combination which has the property of promoting carbon monoxide oxidation at lower temperatures than hydrogen oxidation. In the presence of a catalyst in which gold is dispersed and supported on a certain base metal oxide as ultrafine particles, the inventors of the present invention are completely different from the case of gold alone in the presence of carbon monoxide-containing carbon monoxide in air. The finding that the oxidation, that is, the oxidation of carbon monoxide in the presence of a large excess of oxygen proceeds at a lower temperature than the hydrogen oxidation in the hydrogen-containing air, that is, the hydrogen oxidation in the presence of a large excess of oxygen. (M. Haruta et al., J. Catal. 144 ,
175-192 (1993)). The present inventor, as a result of further research, especially manganese oxide, copper oxide, as a metal oxide carrier,
It was found that when zinc oxide, tin oxide, titanium oxide, nickel oxide or a composite oxide thereof is used, there is a significant difference in the reaction temperature between hydrogen oxidation and carbon monoxide oxidation in the presence of a large excess of oxygen. , It was demonstrated that this property can be stably maintained even in carbon monoxide oxidation in hydrogen, that is, in a reducing gas atmosphere under a large excess of hydrogen. In this case, the activity of the above gold catalyst is not inhibited by the moisture produced by the hydrogen oxidation that occurs concurrently with the carbon monoxide oxidation even in the presence of a large amount of hydrogen [M. Har.
uta et al., “Catalytic Science and Technology”, S. Yo
Shida et al., Vol.1, Kodansha, Tokyo (1991), 331-334
Page] also has the unique property found in the gold-iron oxide catalyst with a large excess of oxygen, which enhances the practicality of the present invention.

In the catalyst used in the present invention, ultrafine particle gold is used in combination with at least one of manganese oxide, copper oxide, zinc oxide, tin oxide, titanium oxide, nickel oxide and a complex oxide of these metals. Is essential, and both exert specific and synergistic effects. That is,
Gold or a metal oxide alone does not exhibit an excellent catalytic action, and the desired performance is exhibited only when the two coexist.

In the gold-metal oxide catalyst, it is necessary to satisfactorily bond the ultrafine gold particles of nm size onto the carrier metal oxide, and it is important to select an appropriate production method. As a method for producing the catalyst, a precipitation-precipitation method (Japanese Patent Publication No. 5-34284,
Japanese Patent Publication No. 6-20559 etc.), Coprecipitation method (Japanese Patent Publication No. 2-2526)
No. 10, Japanese Examined Patent Publication No. 3-12934, Japanese Examined Patent Publication No. 6-29137, etc.) are suitable, and the ordinary catalytic impregnation method does not exhibit the unique catalytic performance required by the present invention. That is, in the catalyst produced by the precipitation-precipitation method and the coprecipitation method,
It is characterized in that ultrafine gold particles having a radius of 10 nm or less are firmly supported on the metal oxide carrier with a relatively uniform distribution. The shape of the metal oxide carrier in the catalyst of the present invention,
The size and the like are not particularly limited, but usually the primary particle diameter is as small as about 10 to 200 nm and the specific surface area is 5
Those having a relatively large value of m ² / g or more are suitable.

The gold / metal atomic ratio in the gold-metal oxide catalyst is preferably about 1/1250 to 1/9, more preferably about 1/196 to 1/19.

Further, as long as it contains the above-mentioned gold-metal oxide, even another form can act as a catalyst suitable for the method of the present invention. For example, when the ultrafine gold particles are held on the metal oxide in the above-mentioned bonded state, a gold-metal oxide conjugate is further added to a commonly used carrier of various shapes such as silica and alimina. By supporting the same, the same desired catalytic action is exhibited.

When carrying out the method of the present invention, the reaction conditions are not particularly limited, but are usually at a temperature of 30 to 2.
The temperature is about 00 ° C. and the pressure is about 1 to 10 atm. The amount of catalyst used is also not particularly limited, but practically, the space velocity (SV) is 1,000 to 50,000 hr ⁻¹ · ml / g.
-It is suitable to use an amount within the range of about cat.

[0019]

INDUSTRIAL APPLICABILITY In the present invention, by using a gold-metal oxide system as a catalyst, it is possible to obtain hydrogen and hydrogen obtained by steam reforming of hydrocarbons such as methane and methanol. Since only carbon monoxide can be selectively oxidized and removed from the gas containing carbon oxide, a hydrogen-containing gas or hydrogen gas required for a solid polymer electrolyte fuel cell or the like can be produced.

[0020]

EXAMPLES Examples of catalyst preparation and practical examples will be shown below to further clarify the features of the present invention.

Catalyst Preparation Example 1 Preparation Example of Gold-Manganese Oxide Catalyst by Coprecipitation Method 0.507 g (1.23 mmol) of chloroauric acid tetrahydrate and 17.2 g (0.06 mol) of manganese nitrate hexahydrate in 1000 ml of distilled water. ) Was dissolved, and this aqueous solution was dissolved in lithium carbonate 5.32 g (0.072 mol) 1000 m
The mixture was added dropwise to the aqueous solution at room temperature and stirred. After stirring was continued for 30 minutes, the supernatant was removed by pouring the mixture, 3000 ml of distilled water was newly added, and after stirring, the supernatant was removed by pouring again. After repeating this washing operation three more times or more, it was filtered, the coprecipitate obtained was vacuum-dried at room temperature for half a day, and calcined in air at 300 ° C. for 5 hours to carry about 5.0 wt% of gold. A gold-manganese oxide catalyst (Au / Mn atomic ratio = 1/49) was obtained.

Catalyst Preparation Example 2 Preparation Example of Gold-Manganese Oxide Catalyst by Coprecipitation Method In 1000 ml of distilled water, 1.30 g (3.16 mmol) of chloroauric acid tetrahydrate and 17.2 g (0.06 mol of manganese nitrate hexahydrate) ) Was dissolved, and the aqueous solution was dissolved in sodium carbonate 7.63 g (0.072 mol) 100
The mixture was added dropwise to a 0 ml aqueous solution at room temperature and stirred. After stirring was continued for 30 minutes, the supernatant was removed by pouring the mixture, 3000 ml of distilled water was newly added, and after stirring, the supernatant was removed by pouring again. After repeating this washing operation three more times or more, it is filtered, and the obtained coprecipitate is vacuum dried at room temperature for half a day, and then dried in air at 300 ° C or 400 ° C.
By calcining at 5 ° C. for 5 hours, a gold-manganese oxide catalyst (Au / Mn atomic ratio = 1/19) carrying about 13% by weight of gold was obtained.

According to observation with a high resolution electron microscope,
In the obtained gold-manganese oxide catalyst, it was confirmed that ultrafine particles of gold of 5 to 20 nm were dispersed and supported on the surface of primary particles of manganese oxide of 20 to 60 nm.

Catalyst Preparation Example 3 Preparation Example of Gold-Manganese Oxide Catalyst by Precipitation and Precipitation Method 0.133 g (0.323 mmol) of chloroauric acid tetrahydrate in 500 ml of distilled water
Was dissolved and heated to 70 ° C, and the pH was adjusted to 8 with 0.1N NaOH aqueous solution.
After that, 5.0 g of manganese oxide (manganese carbonate calcined in air at 400 ° C.) was added all at once with vigorous stirring, and stirring was continued at the same temperature for 1 hour. Then, the mixture is placed at room temperature to remove the supernatant liquid, and 3000 ml of distilled water is newly added,
The mixture was stirred at room temperature for 5 minutes, placed again on the plate, and the supernatant was removed. After repeating this washing operation more than 3 times, it is filtered, and the obtained paste is dried at 90 ° C and calcined in air at 400 ° C for 4 hours to obtain a gold-supported gold of about 1.2% by weight. A manganese oxide catalyst (Au / Mn atomic ratio = 1/196) was obtained.

Catalyst Preparation Example 4 Preparation Example of Gold-Copper Oxide Catalyst by Coprecipitation Method In 1000 ml of distilled water, 1.30 g (3.16 mmol) of chloroauric acid tetrahydrate and 12.0 g (0.06 mol of copper acetate monohydrate) ) Was dissolved, and this aqueous solution was dissolved in 6.05 g (0.072M) of sodium hydrogen carbonate to obtain 1000 ml.
The solution was added dropwise and stirred at 50 ° C. After stirring for 30 minutes,
Dispose of the supernatant and remove the supernatant, add 3000 ml of new distilled water,
After stirring, the solution was placed again and the supernatant was removed. After repeating this washing operation three more times, the mixture was filtered, the obtained coprecipitate was vacuum dried at room temperature for half a day, and calcined in air at 400 ° C. for 5 hours to carry about 13% by weight of gold. A gold-copper oxide catalyst (Au / Cu atomic ratio = 1/19) was obtained.

Catalyst Preparation Example 5 Preparation Example of Gold-Zinc Oxide Catalyst by Coprecipitation Method In 1000 ml of distilled water, 1.30 g (3.16 mmol) of chloroauric acid tetrahydrate and 17.3 g (0.06 mol of zinc sulfate heptahydrate) ) Was dissolved, and this aqueous solution was dissolved in sodium hydroxide 5.28 g (0.132 mol) 1000 m
The mixture was added dropwise to the aqueous solution at 80 ° C and stirred. After stirring was continued for 30 minutes, the supernatant was removed by pouring the mixture, 3000 ml of distilled water was newly added, and after stirring, the supernatant was removed by pouring again. After repeating this washing operation three more times, the mixture was filtered, the obtained coprecipitate was vacuum dried at room temperature for half a day, and calcined in air at 400 ° C. for 5 hours to carry about 13% by weight of gold. A gold-zinc oxide catalyst (Au / Zn atomic ratio = 1/19) was obtained.

Catalyst Preparation Example 6 Preparation Example of Gold-Tin Oxide Catalyst by Coprecipitation Method In 1000 ml of distilled water, 1.30 g (3.16 mmol) of chloroauric acid tetrahydrate and 16.1 g of tin tetrachloride anhydrous (97%) ( 0.06 mol) was dissolved, and this aqueous solution was added dropwise and stirred at 40 ° C. to a 1000 ml aqueous solution in which 36 g (0.288 mol) of ammonia water (concentration 28%) was dissolved. Agitate 30
After continuing the minutes, place the tube on the top to remove the supernatant liquid, and add fresh distilled water 30
After adding 00 ml and stirring, the mixture was placed again on the flask and the supernatant was removed.
After repeating this washing operation three more times, it is filtered,
The coprecipitate obtained is vacuum dried at room temperature for half a day and then heated in air at 400 ° C.
By firing for 5 hours, a gold-tin oxide catalyst (Au / Sn atomic ratio = 1/19) carrying about 6.8% by weight of gold was obtained.

Catalyst Preparation Example 7 Preparation Example of Gold-Titanium Oxide Catalyst by Precipitation and Precipitation Method 0.021 g (0.051 mmol) of chloroauric acid tetrahydrate was dissolved in 100 ml of distilled water and heated to 60 ° C. and 0.1 N NaOH was added. After adjusting the pH to 8 with an aqueous solution, titanium oxide (specific surface area of about 45
5.0 g of m ^{2 /} g) was added at once and stirring was continued for 1 hour at the same temperature. The supernatant was removed by standing at room temperature. Then, 2000 ml of distilled water was newly added, and the mixture was stirred at room temperature for 5 minutes and placed again, and then this washing operation was repeated 3 more times or more, filtered, and the obtained paste was dried at 90 ° C. By calcining at 4 ° C. for 4 hours, a gold-titanium oxide catalyst (Au / Ti atomic ratio = 1/1250) carrying about 0.2% by weight of gold was obtained.

Catalyst Preparation Example 8 Preparation Example of Gold-Nickel Oxide Catalyst by Coprecipitation Method In 1000 ml of distilled water, 0.25 g (0.61 mmol) of chloroauric acid tetrahydrate and 17.5 g (0.06 mol of nickel nitrate hexahydrate) ) Was dissolved, and this aqueous solution was dissolved in potassium carbonate 9.95 g (0.072 mol) 1000 m
The mixture was added dropwise to the aqueous solution at 60 ° C and stirred. After stirring was continued for 30 minutes, the supernatant was removed by placing the mixture in a stirrer, 3000 ml of distilled water was newly added, and after stirring, the supernatant was again removed and the supernatant was removed. After repeating this washing operation three more times or more, it was filtered, the coprecipitate obtained was vacuum dried at room temperature for half a day, and calcined in air at 400 ° C. for 5 hours to carry about 2.6% by weight of gold. A gold-nickel oxide catalyst (Au / Ni atomic ratio = 1/99) was obtained.

Catalyst Preparation Example 9 Preparation of gold-manganese-nickel composite oxide catalyst by coprecipitation method
Preparation example In 1000 ml of distilled water, 2.75 g (6.7 mmol) of chloroauric acid tetrahydrate and 11.5 g (0.04 mol) of manganese nitrate hexahydrate and nickel nitrate
Dissolve 5.8 g (0.02 mol) of hexahydrate, and add this aqueous solution to a 1000 ml aqueous solution containing 8.5 g (0.0804 mol) of sodium carbonate.
The mixture was dropped and stirred at ℃. After stirring was continued for 30 minutes, the supernatant was removed by placing the mixture in a stirrer, 3000 ml of distilled water was newly added, and after stirring, the supernatant was again removed and the supernatant was removed. After repeating this washing operation three more times, the mixture was filtered, the coprecipitate obtained was vacuum dried at room temperature for half a day, and calcined in air at 400 ° C. for 5 hours to carry about 28% by weight of gold. A gold-manganese oxide-nickel oxide catalyst (Au / (Mn + Ni) atomic ratio = 1/9) was obtained.

Example 1 0.20 g of the gold-manganese oxide catalyst (70 to 120 mesh) obtained in the above catalyst preparation examples 1 and 2 was placed in a U-shaped quartz reaction tube having an inner diameter of 6 mm and having a thermocouple sheath inside. Fix the catalyst layer temperature
After heat pretreatment at 250 ° C for 30 minutes in air flow, hydrogen 1
Conversion of hydrogen or carbon monoxide at various catalyst bed temperatures by circulating an air mixed gas containing 1% by volume or 1% by volume of carbon monoxide at a flow rate of 2000 ml / hr and analyzing the outlet gas online by gas chromatography. The rate was calculated after the steady state was reached. The reaction results are shown in FIG.

In FIG. 1, curve 1 shows the oxidation reaction of carbon monoxide by the gold-manganese oxide catalyst (Au / Mn atomic ratio = 1/49) obtained in Catalyst Preparation Example 1, and curve 2 shows the same gold. -Showing an oxidation reaction of hydrogen with a manganese oxide catalyst. Curve 3 shows the gold-manganese oxide catalyst (Au) obtained in Catalyst Preparation Example 2.
/ Mn atomic ratio = 1/19) shows the oxidation reaction of carbon monoxide, and curve 4 shows the oxidation reaction of hydrogen with the same gold-manganese oxide catalyst.

As is apparent from FIG. 1, when the gold-manganese oxide catalyst is used, the carbon monoxide oxidation reaction occurs at a much lower temperature than the hydrogen oxidation reaction, and the monoxide oxidation in hydrogen occurs. It is advantageous for selective oxidation of carbon. This is in contrast to platinum-based catalysts, palladium-based catalysts, and the like, which show higher activity for hydrogen oxidation.

Example 2 Using the gold-metal oxide catalysts obtained in Catalyst Preparation Examples 3 to 9,
The catalyst activity was measured in the same manner as in Example 1. The result shows that the conversion rate of hydrogen or carbon monoxide is 50%.
The _results are summarized in Table 1 by the temperature T _1/2 reaching the temperature.

[0035]

[Table 1]

As is clear from Table 1, manganese oxide,
Copper oxide, zinc oxide, tin oxide, gold catalyst titanium oxide or nickel oxide and carrier, T _1/2 of the hydrogen oxidation considerably higher than T _1/2 carbon monoxide oxidation. On the other hand, when gold was supported on alumina or silica (Comparative Examples 1 and 2), such characteristics were not observed, and the platinum-titanium oxide catalyst (Comparative Example 3) and the palladium-alumina catalyst (Comparative Example) were compared. In Example 4), the hydrogen oxidation T _1/2 is much lower.

Example 3 In the same manner as in Example 1, the gold-manganese oxide catalyst obtained in Catalyst Preparation Example 2 was used, and the catalyst layer temperature was variously changed to 1% by volume of carbon monoxide and 1% by volume of oxygen. When a reaction was carried out by circulating hydrogen gas containing and, the results were shown in FIG. 2 (calcination temperature 300 ° C. during catalyst preparation) and FIG. 3 (calcination temperature 40 during catalyst preparation).
The results shown in (0 ° C.) were obtained.

As is clear from FIG. 2, whether the calcination temperature during preparation is 300 ° C. or 400 ° C., the reaction temperature of 50-80 ° C. is 95% when the catalyst of the present invention is used. %
The above CO oxidation reaction rates are obtained, and it is clear that the reaction temperature is lower by about 150 ° C. or more and the CO oxidation reaction rate is higher than that of the platinum-based noble metal catalyst.

Regarding the stability of the catalyst of the present invention in the presence of a large excess of hydrogen, it is clear from FIG. 3 that the catalyst of the present invention is sufficiently resistant to long-term use at 120 ° C., where reduction degradation of hydrogen is more likely to occur. ing.

Example 4 The oxidation reaction rate of carbon monoxide in hydrogen was determined for the catalysts obtained in Catalyst Preparation Examples 1 and 3 to 9 in the same manner as in Example 3. The results are shown in Table 2.

[0041]

[Table 2]

From the results shown in Table 2, it is clear that carbon monoxide in hydrogen can be selectively oxidized and removed in the range of 30 to 200 ° C. by selecting the kind of metal oxide carrier and the amount of gold supported. .

[Brief description of drawings]

FIG. 1 is a graph showing that the gold-manganese oxide catalyst according to the present invention promotes the oxidation of carbon monoxide more than the oxidation of hydrogen at low temperature.

FIG. 2 is a graph showing that the gold-manganese oxide catalyst according to the present invention selectively oxidizes carbon monoxide in hydrogen containing carbon monoxide at low temperature.

FIG. 3 is a graph showing that the gold-manganese oxide catalyst according to the present invention selectively oxidizes carbon monoxide in hydrogen containing carbon monoxide at low temperature.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Rosa Maria Torres Sanchez de Kurt Argentina Buenos Aires Manuel Bae Gonnet (Sae Pa 1897) Centenario Entre 505 I 508 Centro de Technolohia de Lecruzos Minerales Is Ceramica (72) Inventor Koji Tanaka 1-831 Midorigaoka, Ikeda-shi, Osaka Prefecture Industrial Technology Institute Osaka Industrial Technology Research Institute

Claims (4)

[Claims] 1. A method for selectively oxidizing and removing carbon monoxide from a gas containing hydrogen and carbon monoxide in the presence of a gold catalyst. 2. The method according to claim 1, wherein the gold catalyst is a catalyst in which ultrafine gold particles are dispersed and supported on a metal oxide. 3. The metal oxide is at least one of manganese oxide, copper oxide, zinc oxide, tin oxide, titanium oxide, nickel oxide and a composite oxide of these metals.
Or the method described in 2. 4. A catalyst for removing carbon monoxide from a gas containing hydrogen and carbon monoxide, wherein ultrafine gold particles are dispersed and supported on a metal oxide.