JP2003251181A - Catalyst for removing carbon monoxide in hydrogen gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a catalyst for removing CO having an effect to suppress a methanation reaction in which catalyst activity is high when used to remove CO contained in a hydrogen rich gas, such as a reformed gas, by converting to CO<SB>2</SB>by the reaction of a water gas shift, and in which the CO is converted to CH<SB>4</SB>in a high temperature region. <P>SOLUTION: This catalyst for removing carbon monoxide in the hydrogen rich gas is characterized in that platinum and/or platinum oxide and rhenium and/or rhenium oxide are supported on a carrier comprising titania or a metal oxide containing the titania. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CO-removing catalyst used for removing CO contained in a hydrogen-rich gas such as a reformed gas by converting it to CO ₂ by a water gas shift reaction. .

[0002]

2. Description of the Related Art In recent years, improvements in polymer electrolyte fuel cells have been drawing attention. A polymer electrolyte fuel cell supplies hydrogen (fuel) to the anode side and oxygen or air (oxidizer) to the cathode side to cause a reaction through a solid electrolyte membrane (proton conductive membrane) and generate an electric current. I will get it. As the electrode catalyst, platinum black is used for both the anode and cathode, and a catalyst in which platinum or a platinum alloy is supported on carbon is used. However, when the hydrogen (fuel) contains CO, even if a small amount of this electrode catalyst is used, It is known that it is poisoned and the battery performance is significantly deteriorated.

As a method for removing CO in hydrogen gas, oxygen is introduced into the reaction system in the presence of a catalyst to selectively oxidize and remove CO into CO ₂ (the following formula (1)), and A method (the following formula (2)) in which water (H ₂ O) is added to the reaction system to cause a water gas shift reaction in the presence of a catalyst is known. [CO oxidation reaction] CO + 1 / 2O ₂ → CO ₂ (1) [water gas shift reaction] CO + H ₂ O ⇔ CO ₂ + H ₂ (2) (ΔH = -41 kJ / mol)

In the former method, when the hydrogen concentration in the reaction system is high, the oxygen introduced into the system reacts with a large amount of hydrogen present in the system as shown in the following formula (3). ,
A highly selective catalyst is needed. H ₂ + 1 / 2O ₂ → H ₂ O (3)

On the other hand, the water gas shift reaction in which water is added to the reaction system is widely known as a method for producing hydrogen (see Japanese Patent Laid-Open No. 2000-302405). A feature of this method is that it is generally carried out by combining processes at two reaction temperatures. That is, depending on the reaction temperature, it is called a high temperature shift reaction and a low temperature shift reaction. The high temperature shift reaction is performed at about 400 ° C, and the low temperature shift reaction is performed at about 250 ° C. Since the water gas shift reaction is an exothermic reaction as shown in the above formula (2),
Equilibrium is advantageous in carrying out the reaction at low temperature for hydrogen production, but there is a problem that the reaction rate becomes slow.
Therefore, at high temperature, it is disadvantageous in equilibrium, but since the reaction rate is fast, first, a large amount of CO is converted to CO ₂ at high temperature,
Then, the CO remaining at a low temperature is treated so as to have a further lower concentration, which is usually a two-step process. An iron-chromium-cobalt type catalyst has been conventionally known as a catalyst used for this high temperature shift reaction, and a copper-zinc type catalyst has been conventionally known as a catalyst used for a low temperature shift reaction (Japanese Patent Publication No. 59-46883). Japanese Patent Laid-Open Publication No. 53-141191).

Recently, it has been known that a catalyst in which platinum, platinum-rhenium or the like is supported on a zirconia carrier as a catalyst for low temperature shift reaction has higher activity than conventional copper-zinc catalysts (patent). (See Japanese Patent No. 3215680). However, when the aquatic gas shift reaction is performed in the high temperature range (around 350 ° C.) using the catalyst, it is insufficient to suppress the side reaction of producing methane by the CO methanation reaction represented by the following formula (4). Therefore, there is a problem that hydrogen generation efficiency is reduced. [Methanation Reaction] CO + 3H ₂ → CH ₄ + H ₂ O (4) This side reaction is extremely unfavorable when CO-free hydrogen is to be obtained in a high yield by a water gas shift reaction. Therefore, as a catalyst for aquatic gas shift reaction, CO that suppresses the methanation reaction and has high activity
A removal catalyst has been desired.

[0007]

An object of the present invention is to provide a catalyst which is highly active in the above water gas shift reaction, can suppress the methanation reaction, and can effectively reduce the CO concentration in hydrogen gas. Is to provide.

[0008]

In order to solve the above-mentioned problems, the present invention provides a carrier comprising titania or a metal oxide containing titania, platinum and / or platinum oxide,
Also provided is a catalyst for removing carbon monoxide in hydrogen gas, which is characterized by supporting rhenium and / or rhenium oxide.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The carbon monoxide removing catalyst of the present invention will be described in detail below. [Carrier] The carrier used in the present invention is titania or a metal oxide to which titania is added, and in any case, a granular or pellet-like porous material having a particle size of about 2 to 4 mmφ is usually used. Is used.

When a metal oxide added with titania is used as the carrier, examples of the metal oxide include zirconia, alumina, silica, silica-alumina, zeolite and ceria. Among them, catalyst preparation is possible. It is preferable to use zirconia or alumina because it is relatively easy.

As a method of adding titania to the above metal oxide, an aqueous solution of a titanium compound such as titanium potassium oxalate dihydrate, titanium chloride or titanium sulfate or a titania sol is added to the metal oxide in the form of metal oxide. Then, the titanium compound is impregnated in the granular metal oxide, dried, and then fired at a temperature of usually 200 to 700 ° C., preferably 300 to 600 ° C. for about 10 minutes to 3 hours. As a result, a metal oxide containing titania can be obtained.

The amount of titania contained in the particulate titania-containing metal oxide thus obtained is usually 0.1 to 50.0.
% By weight, preferably 0.1-20.0% by weight, particularly preferably
0.1 to 10.0% by weight. If the titania content is too low, the effect of improving the water gas shift reaction activity is not sufficient,
In addition, if the suppression of the methanation reaction becomes insufficient, and if it is too large on the contrary, further improvement of the above effects cannot be expected, and the advantage of economy is lacking.

[Carrying of Catalytically Active Component] Platinum and / or platinum oxide which is a catalytically active component, and
By supporting rhenium and / or rhenium oxide,
The CO removal catalyst of the present invention can be obtained. Platinum and / or platinum oxide in the catalyst, and, as the supported amount of rhenium and / or rhenium oxide, platinum and / or platinum oxide is usually 0.01 to 20.0% by weight, relative to the weight of the catalyst. Preferably 0.01 to 10.0% by weight,
It is particularly preferably 0.1 to 5.0% by weight, and rhenium and / or rhenium oxide is usually 0.01 to 20.0% by weight, preferably 0.01 to 10.0% by weight, particularly preferably 0.
It is 1 to 5.0% by weight. Platinum and / or platinum oxide,
In addition, if the content of rhenium and / or rhenium oxide is too low, it is difficult to obtain sufficient catalytic activity when CO in hydrogen gas is converted to CO ₂ by a water gas shift reaction and removed. If the amount is too large, further improvement in catalytic activity cannot be expected, and use of a noble metal is disadvantageous in terms of economy.

The ratio of platinum and / or platinum oxide to rhenium and / or rhenium oxide used as a catalyst is usually Pt / Re in terms of metal atom weight ratio.
= 4/1 to 1/4, preferably 3/1 to 1/3, particularly preferably 2/1 to 1/2.

The method of loading platinum and / or platinum oxide and rhenium and / or rhenium oxide on the carrier is not particularly limited, and a known method can be adopted. For example, dinitrodiammine platinum [Pt (N
A nitric acid solution of [O ₂ ) ₂ (NH ₃ ) ₂ ] or an aqueous solution of chloroplatinic acid hexahydrate or the like is dropped and impregnated into the above carrier, and then dried. Next, for example, an aqueous solution of a rhenium compound such as ammonium perrhenate, perrhenic acid, rhenium oxide, or rhenium chloride is dropped and impregnated in the same manner, and then dried. The treatment with the rhenium compound solution may be performed first, and then the treatment with the platinum compound solution may be performed. Next, by firing at a temperature of 300 to 700 ° C., preferably 400 to 600 ° C. for about 30 minutes to 2 hours, platinum and / or platinum oxide as the metal supported on the carrier, and Presence of rhenium and / or rhenium oxide.

[Characteristics of the catalyst of the present invention] The catalyst of the present invention obtained as described above employs titania or a metal oxide to which titania is added as a carrier, so that CO due to a water gas shift reaction of platinum and rhenium is adopted. CO
_{It is possible} to improve the catalytic activity of conversion / removal to ₂ , and to suppress the methanation reaction.

[0017]

[Examples] Example-1 Zirconia granular carrier (manufactured by Daiichi Rare Element Chemical Industry Co., Ltd .: RSC-
(HP) 100 g was placed in a container, 27 mL of an aqueous solution of potassium titanium oxalate (concentration: 40% by weight) was dropped and impregnated, and left for 1 hour after completion of dropping. Then, using a dryer, in air 11
It was dried at 0 ° C for 2 hours. Further, the temperature was raised from room temperature to 500 ° C. in a baking furnace in 1 hour, and a baking treatment (in air) was carried out at 500 ° C. for 1 hour to prepare a zirconia granular carrier containing 2% by weight of titania.

97 g of the granular carrier obtained above was placed in a container, and 27 mL of dinitrodiammine platinum nitric acid solution (concentration: 7.4% by weight, platinum metal equivalent: 2.0 g) was added dropwise and impregnated, and left for 1 hour after the completion of the addition. did. Then, using a dryer, it was dried in air at 110 ° C. for 2 hours. The dried product was put in a container, and 27 mL of an ammonium perrhenate aqueous solution (concentration: 3.7% by weight, rhenium metal conversion: 1.0 g) was dropped and impregnated,
After completion of dropping, the mixture was left for 1 hour. Then, using a dryer, it was dried in air at 110 ° C. for 2 hours.

Then, from room temperature to 500 ° C. in the firing furnace.
The temperature is raised to 1 hour, and a calcination treatment (in air) at 500 ° C for 1 hour is performed to obtain a zirconia granular carrier (titania 2% by weight).
Platinum (2% by weight) and rhenium (1% by weight)
100 g of a CO-removing catalyst on which was carried was prepared.

Comparative Example-1 In the same manner as in Example-1, except that titania was not supported on zirconia, platinum (2% by weight) and rhenium (1% by weight) were supported on a zirconia granular carrier to remove CO. 100 g of catalyst (for comparison) was prepared.

Example-2 100 g of alumina granular carrier (KHA-24, manufactured by Sumitomo Chemical Co., Ltd.) was placed in a container, and 27 mL of an aqueous potassium potassium oxalate solution (concentration: 40% by weight) was added dropwise and impregnated, and the addition was completed. After that, it was left for 1 hour. Then, using a dryer, it was dried in air at 110 ° C. for 2 hours. Furthermore, from room temperature to 500 ° C in the firing furnace 1
The temperature was raised over time, and a calcination treatment (in air) at 500 ° C. for 1 hour was performed to prepare an alumina granular carrier containing 4% by weight of titania.

97 g of the granular carrier obtained above was placed in a container, 38 mL of dinitrodiammine platinum nitric acid solution (concentration: 5.3% by weight, platinum metal equivalent: 2.0 g) was added dropwise and impregnated, and left for 1 hour after completion of the addition. did. Then, using a dryer, it was dried in air at 110 ° C. for 2 hours. The dried product was placed in a container, and 38 mL of an ammonium perrhenate aqueous solution (concentration: 2.7% by weight, rhenium metal conversion: 1.0 g) was dropped and impregnated,
After completion of dropping, the mixture was left for 1 hour. Then, using a dryer, it was dried in air at 110 ° C. for 2 hours.

Then, from room temperature to 500 ° C. in the firing furnace.
The temperature is raised to 1 hour, and a calcination treatment (in air) at 500 ° C. for 1 hour is performed, and platinum (2% by weight) and rhenium (1% by weight) are supported on the alumina granular carrier (containing 4% by weight of titania). 100 g of the CO removing catalyst was prepared.

Comparative Example-2 Example except that alumina does not carry titania.
In the same manner as in -2, 100 g of a CO-removing catalyst (for comparison) in which platinum (2 wt%) and rhenium (1 wt%) were supported on a zirconia granular carrier was prepared.

Example 3 Titania Granular Carrier (Sakai Chemical Industry Co., Ltd .: CS-300S-24) 97
20 g of dinitrodiammine platinum nitric acid solution (concentration: 10% by weight, platinum metal conversion: 2.0 g) was dropped and impregnated in the container, and left for 1 hour after the dropping was completed. Then, using a dryer, it was dried in air at 110 ° C. for 2 hours. The dried product was placed in a container, 20 mL of an aqueous ammonium perrhenate solution (concentration: 5.0% by weight, rhenium metal conversion: 1.0 g) was added dropwise and impregnated, and left for 1 hour after completion of the addition. Then, using a dryer, it was dried in air at 110 ° C. for 2 hours.

Then, from room temperature to 500 ° C. in the firing furnace.
The catalyst for CO removal in which platinum (2% by weight) and rhenium (1% by weight) are supported on the titania granular carrier after heating to 500 ° C for 1 hour (in air)
100 g was prepared.

Comparative Example-3 Titania granular carrier (Sakai Chemical Industry Co., Ltd .: CS-300S-24) 98
20 g of dinitrodiammine platinum nitric acid solution (concentration: 10% by weight, platinum metal conversion: 2.0 g) was dropped and impregnated in the container, and left for 1 hour after the dropping was completed. Then, using a dryer, it was dried in air at 110 ° C. for 2 hours. Subsequently, the temperature is raised from room temperature to 500 ° C in a firing furnace in 1 hour, and the temperature is 500 ° C ×
A calcination treatment (in air) was carried out for 1 hour to prepare 100 g of a CO removing catalyst (for comparison) in which platinum (2% by weight) was supported on a titania granular carrier.

Table 1 summarizes the catalyst compositions of Examples -1 to 3 and Comparative Examples -1 to 3 above.

[0029]

[Table 1]

[Evaluation] The catalysts of Examples -1 to -3 and Comparative Examples -1 to -3 were evaluated for CO removal performance and the like. [Evaluation method] A reaction tube having a volume of 15.0 mL was filled with the above catalyst, and a mixed gas of H ₂ (20% by volume) and N ₂ (80% by volume) was flown to raise the temperature from room temperature to 300 ° C in 30 minutes. After 1
The same temperature was maintained for a period of time for reduction treatment.

Next, the mixed gas was switched to N ₂ gas, the heating was stopped, and the temperature was lowered to 100 ° C. or lower. When the temperature drops below 100 ° C, the supply of N ₂ gas is stopped, and then H ₂ (8
A mixed gas of 0% by volume, CO ₂ (12% by volume) and CO (8% by volume) was supplied under the condition that the SV (blank speed) was 10,000 (h ⁻¹ ). H ₂ O (steam) was added to this mixed gas as H ₂ O / CO =
In order to satisfy the condition of 4.2 (volume ratio), the catalyst temperature was raised to 200 ° C, and the CO concentration (volume%) at the reaction tube outlet was changed to H ₂ in a steady state where the temperature was maintained at 200 ° C. Under the measurement conditions except O, the measurement was performed using a gas analyzer (Bex-2201E manufactured by Best Sokki Co., Ltd.) using the non-dispersion infrared method as a measurement principle.

In the same manner, the measurement was carried out also when the catalyst temperatures were 250 ° C., 300 ° C. and 350 ° C. When the catalyst temperature was 350 ° C., the CH ₄ content (ppm) at the outlet of the reaction tube was measured using the same method and the same measuring instrument.

[Measurement Results and Analysis] The above measurement results for the catalysts of Examples and Comparative Examples are shown in FIGS. From FIG. 1 and FIG. 2, an example in the case of a catalyst using a zirconia or alumina granular support added with titania
-1 and Example-2 were confirmed to have the effect of reducing the CO concentration by adding titania. From FIG. 3, an example in the case of a titania granular carrier catalyst supporting rhenium
Regarding -3, the effect of reducing the CO concentration by using rhenium together with platinum was confirmed.

Regarding the CH ₄ concentration indicating that a methanation reaction is occurring as a side reaction, the results of the measurement shown in FIG. 4 indicate that an example in the case of a catalyst using a titania-added zirconia or alumina granular carrier was used. It was confirmed that the methanation reaction was suppressed to be low for -1 and Example-2. Also in the case of Example-3 in the case of the titania granular carrier catalyst supporting rhenium, the amount of CH is slightly more than that in the case of the catalyst using the zirconia or alumina granular carrier in which titania is added. _{4 Although the} concentration is high, it can be seen that the methanation reaction is suppressed to be significantly lower than that of Comparative Example-1 and Comparative Example-2 in the case of a catalyst using a zirconia or alumina granular carrier to which titania is not added. .

Therefore, the catalyst for removing CO according to the present invention is
In the aquatic gas shift reaction, the methanation reaction can be suppressed in the high temperature range (350 ° C.) and the activity of the shift reaction can be maintained high.

[0036]

INDUSTRIAL APPLICABILITY The catalyst for CO removal of the present invention can maintain high catalytic activity when CO contained in hydrogen-rich gas such as reformed gas is converted into CO ₂ by aquatic gas shift reaction and removed. it can. Furthermore, CO is CH in the high temperature range.
_It also has the effect of suppressing the methanation reaction of being converted to ₄ . The CO removing catalyst of the present invention is useful, for example, for producing hydrogen gas as a fuel for fuel cells.

[Brief description of drawings]

FIG. 1 is a diagram showing CO removal performance of catalysts obtained in Example-1 and Comparative Example-1 at respective catalyst temperatures.

FIG. 2 is a diagram showing the CO removal performance of the catalysts obtained in Example-2 and Comparative Example-2 at respective catalyst temperatures.

FIG. 3 is a diagram showing CO removal performance of the catalysts obtained in Example-3 and Comparative Example-3 at respective catalyst temperatures.

FIG. 4 shows Example-1 to Example-3 and Comparative Example-
It is a figure which shows the methanation reaction suppression performance in the catalyst temperature of 350 degreeC of the catalyst obtained in 1-Comparative example-3.

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[Procedure amendment]

[Submission date] July 3, 2002 (2002.7.3)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

Example-2 100 g of alumina granular carrier (KHA-24 manufactured by Sumitomo Chemical Co., Ltd.) was placed in a container, and 50 mL of an aqueous solution of potassium titanium oxalate (concentration: 40% by weight) was added dropwise and impregnated. After that, it was left for 1 hour. Then, using a dryer, it was dried in air at 110 ° C. for 2 hours. Furthermore, from room temperature to 500 ° C in the firing furnace 1
The temperature was raised over time, and a calcination treatment (in air) at 500 ° C. for 1 hour was performed to prepare an alumina granular carrier containing 4% by weight of titania.

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Claims (4)

[Claims] 1. A carrier comprising titania or a metal oxide containing titania, platinum and / or platinum oxide,
And a catalyst for removing carbon monoxide in hydrogen gas, which comprises rhenium and / or rhenium oxide. 2. The catalyst according to claim 1, wherein the titania content in the titania-containing metal oxide is 0.1 to 20.0% by weight. 3. The amount of platinum and / or platinum oxide supported on the carrier is 0.01 to 10.0 weight based on the weight of the catalyst supporting platinum and / or platinum oxide and rhenium and / or rhenium oxide. %, And the supported amount of rhenium and / or rhenium oxide is 0.01
~ 10.0% by weight, characterized in that 1 or 2
The catalyst according to 1. 4. The catalyst according to claim 1, wherein the metal oxide is one or more metal oxides selected from the group consisting of alumina and zirconia.