JP2003135960A - Shift catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique to improve the activity of a shift reaction. SOLUTION: Following shift catalyst is used. The shift catalyst has a catalytic substance consisting of an active seed having the activity to promote the shift reaction and an auxiliary component having a function to hold the active seed, and further has a water vapor adsorbing substance which can adsorb water vapor. By using the above shift catalyst, water vapor in the gas supplied to the shift reaction is withdrawn to the water vapor adsorbing substance to increase the concentration of water vapor near the active seed, which further promotes the shift reaction. Thus, the activity of the shift reaction can be improved.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a shift catalyst having an activity of promoting a shift reaction of producing hydrogen and carbon dioxide from water and carbon monoxide, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, such a shift catalyst has been used, for example, to reduce the concentration of carbon monoxide in the fuel gas supplied to the fuel cell. As a method for generating a fuel gas to be supplied to a fuel cell, there is known a method of reforming a raw fuel such as hydrocarbon or alcohol to make a hydrogen-rich gas. However, the hydrogen-rich gas generated by the reforming reaction is It usually contains a certain amount of carbon monoxide. Since carbon monoxide has a property of poisoning an electrode catalyst of a fuel cell, when supplying the hydrogen-rich gas as a fuel gas to the fuel cell, a carbon monoxide is used to shift the amount of hydrogen in the hydrogen-rich gas using a shift catalyst or the like. The concentration of carbon oxide has been reduced. The formula (1) below represents a shift reaction promoted by the shift catalyst.

CO + H ₂ O → CO ₂ + H ₂ +40.5 (kJ / mol) (1)

As the shift catalyst, a Cu / Zn type catalyst,
Known are Cu-based catalysts such as Cu / Zn / Al-based catalysts and Cu / Cr-based catalysts, and precious metal catalysts including precious metals such as platinum. For example, Japanese Patent Application Laid-Open No. 2-174936 discloses a Cu / Zn / Al-based catalyst containing barium carbonate.

[0005]

When a polymer electrolyte fuel cell is used as the fuel cell, the carbon monoxide concentration in the fuel gas supplied to the fuel cell is usually required to be several ppm or less. It is desirable to keep the carbon monoxide concentration in the fuel gas low. Further, when the fuel cell is used as a power source for driving an electric vehicle, the space in which the fuel cell system can be mounted is limited. Is desired. Therefore, in order to meet these requirements, a shift catalyst having a higher activity of promoting the shift reaction has been desired.

The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to provide a technique for improving the activity of shift reaction.

[0007]

Means for Solving the Problem and Its Action / Effect To achieve the above object, the present invention provides a shift catalyst having an activity of promoting a shift reaction of producing hydrogen and carbon dioxide from water and carbon monoxide. The gist is to provide a catalyst substance containing an active species having an activity of promoting the shift reaction and a water vapor adsorbing substance capable of adsorbing water vapor.

As described above, by providing the catalytic substance containing the active species and the water vapor adsorbing substance capable of adsorbing water vapor, the water vapor in the gas subjected to the shift reaction is attracted to the water vapor adsorbing substance, The water vapor concentration around the active species existing near the water vapor adsorbing substance increases,
The shift reaction is further promoted. Therefore, the catalytic activity of the shift catalyst can be improved.

In the shift catalyst of the present invention, the catalyst substance may contain a noble metal acting as the active species and an oxide carrying the noble metal.

In such a shift catalyst of the present invention,
The active species may not exist substantially on the water vapor adsorbing substance but may exist on the oxide.

Further, in the shift catalyst of the present invention, the catalyst substance may be a mixture of a plurality of components containing a metal acting as the active species. Here, the mixture forming the catalyst substance may be, for example, a composite compound (composite oxide or the like) of a plurality of metals containing a metal that acts as an active species. Such complex compounds are
For example, it can be manufactured by a coprecipitation method. Alternatively,
At least a part of the mixture may be in a state (solid solution) in which a plurality of elements are uniformly distributed. Further, it may be a simple mixture of a metal such as an active species or a compound such as a metal oxide, and another substance.

In the shift catalyst of the present invention, a first layer formed on a predetermined substrate and containing the water vapor adsorbing substance, and a second layer formed on the first layer and containing the catalyst substance. It is also possible to have a layer.

The present invention can be implemented in various modes other than those described above, for example, a carbon monoxide reducing device equipped with a shift catalyst, a fuel reforming device equipped with this carbon monoxide reducing device, Alternatively, it can be realized by a fuel cell system, a shift catalyst manufacturing method, or the like.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A. First Embodiment: FIG.
FIG. 5 is a process diagram illustrating a method of manufacturing a shift catalyst according to the first embodiment of the present invention. In the present embodiment, first, an auxiliary component having a function of holding a substance to be an active species and a water vapor adsorbing substance capable of adsorbing water vapor are prepared (step S100). Here, as the active species having the activity of promoting the shift reaction, for example, platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (R
A noble metal containing at least one of u) and iridium (Ir) can be used. Particularly, when platinum is used as a noble metal which is an active species, it is preferable because a catalyst having higher activity can be produced.

As the auxiliary component prepared in step S100, when the above-mentioned noble metal is used as the active species, titania, zirconia, cerium oxide, silicon oxide, alumina or other oxide can be used. When these oxides are used as an auxiliary component, these oxides not only have the function of retaining a substance that becomes an active species, but also exert the effect of affecting the shift reaction and increasing the catalytic activity. As an oxide used as such an auxiliary component, titania is particularly excellent, and it becomes possible to further improve the activity of the shift catalyst.

The water vapor adsorbing substance is one having a function of attracting water vapor when the shift reaction proceeds, and for example, zeolite can be used. Zeolite has a three-dimensional network structure, and various zeolites having different pore sizes formed by this network structure are known. For example, there are ZSM-5, zeolite β, mordenite, ferrierite and the like. As such a zeolite, not only natural zeolite but also synthetic zeolite artificially synthesized from coal ash may be used. It is desirable that the auxiliary component and the water vapor adsorbing substance prepared in step S100 have a shape such that they can be easily mixed, such as powder.

Next, the auxiliary component prepared in step S100 and the water vapor adsorbing substance are mixed (step S11).
0), the resulting mixture is immersed in an active species solution containing active species (step 120). When the noble metal as described above is used as the active species, the solution of the noble metal salt may be used as the active species solution used in step S120. A water-soluble solution such as a nitrate solution can be used as the noble metal salt solution. Next, the mixture immersed in the active species solution is heated and dried (step S13).
0), evaporating the water content of the active species solution. After that, it is further fired (step S140) and evaporated to dryness,
A treatment for supporting the active species on the auxiliary component and the water vapor adsorbing substance is performed.

After the firing step of step S140, the shift catalyst is completed by forming it into a predetermined shape (step S150). The shift catalyst may have a pellet shape, for example. As a method of forming into pellets, there is a method of compressing the fired product obtained in step S140 and further crushing this.

As described above, by providing the catalytic substance composed of the active species having the activity of promoting the shift reaction and the auxiliary component having the function of holding the active species, and the water vapor adsorbing substance capable of adsorbing the water vapor, it is possible to further improve the catalyst. It can be a highly active shift catalyst. A state of the shift catalyst manufactured according to the manufacturing process shown in FIG. 1 is schematically shown in FIG. In this shift catalyst, catalytic species are carried on the surfaces of both the auxiliary component and the water vapor adsorbing substance. A water vapor adsorbing substance such as zeolite has a property of attracting water vapor in a gas when performing a shift reaction. When water vapor is attracted to the water vapor adsorbing substance, the water vapor concentration around the active species existing in the vicinity of the water vapor adsorbing substance increases. As shown in the equation (1), the shift reaction is a reaction between carbon monoxide and water. Therefore, by increasing the water vapor concentration around the active species,
It is considered that the shift reaction is promoted.

In particular, when zeolite is used as the water vapor adsorbing substance, it is possible to obtain an effect that it is possible to prevent a shortage of water vapor when the shift reaction proceeds and to maintain the activity of the shift reaction. It is thought to be done.
Zeolite can adsorb water vapor (water molecules) in the pores of a three-dimensional network structure formed by aluminum, silicon, and oxygen atoms, and retain it as water of crystallization. It adsorbs or releases water vapor depending on the water vapor partial pressure or temperature. Zeolite has a strong adsorptive power for adsorbing water vapor, compared with general physical adsorption, and can effectively retain water vapor,
At a predetermined high temperature at which the shift reaction proceeds, it is possible to release the water vapor with good response as the water vapor partial pressure decreases.
Therefore, when the partial pressure of water vapor in the gas used for the shift reaction is lower than the surrounding partial pressure of water vapor when the adsorption / release state of water vapor in the zeolite is in an equilibrium state, the zeolite releases water vapor, and this water vapor It is possible to proceed the shift reaction by utilizing Therefore, when the amount of water vapor used for the shift reaction is insufficient, it is possible to prevent the activity of the shift reaction from decreasing due to the insufficient amount of water vapor. This makes it possible to keep the activity of the shift reaction sufficiently high.

Here, as a method for supporting the active species on the mixture of the auxiliary component and the water vapor adsorbing substance, different methods such as an ion exchange method other than the above-mentioned evaporation to dryness (impregnation method) are used. Is also good.

In the first embodiment described above, the active species are supported on the mixture of the powdery auxiliary component and the water vapor adsorbing substance, and then the mixture is molded into pellets or the like. However, the molding may be performed before the supporting. That is, the auxiliary component and the water vapor adsorbing substance are mixed, and a process of forming this into a pellet shape is performed first, and thereafter, the pellet is immersed in the active species solution described above to carry the active species. Good as a matter.

B. Second Embodiment: In the first embodiment described above, the active species is carried on the auxiliary component, but the component having a function of retaining the active species and the active species exist in a mixed state. The present invention can also be applied to a shift catalyst that does this. FIG. 3 is a process diagram showing a method of manufacturing a shift catalyst according to the second embodiment of the present invention. In the present embodiment, first, a catalyst substance containing a substance to be an active species is prepared (step S200). As the catalyst substance prepared in this step S200, a mixture of a plurality of components containing a metal acting as an active species is used. For example, a copper-based catalyst such as a copper-zinc catalyst (Cu-Zn catalyst) can be used. The Cu-Zn catalyst can be produced by coprecipitating copper oxide and zinc oxide by a well-known coprecipitation method. In the Cu-Zn catalyst, copper (Cu) is the active species. By coprecipitating copper oxide with zinc oxide, C which is a catalyst substance with a stable structure
It can be a u-Zn catalyst. Further, copper, which is an active species, is Cu-Zn which is a mixture of such plural components.
By using the catalyst, not only the structure as the catalyst is stabilized but also sufficient activity as the shift catalyst can be secured. Other components may be mixed in the catalyst substance prepared in step S200. For example, when a Cu-Zn catalyst is produced by the coprecipitation method as described above, alumina can be coprecipitated with copper oxide and zinc oxide to allow the alumina to be mixed. Further, as another catalyst substance prepared in step S200, an iron-chromium catalyst (Fe-Cr catalyst) can be cited. The Fe-Cr catalyst can also be produced by the coprecipitation method as described above.

When the catalyst substance is prepared, a water vapor adsorbing substance is further prepared (step S210). As the water vapor adsorbing substance, various kinds of zeolite can be used as in the first embodiment. Next, step S200.
The catalyst substance prepared in step S210 and the water vapor adsorbing substance prepared in step S210 are mixed (step S220).
For example, when the catalyst substance is manufactured by the coprecipitation method in step S200, the catalyst substance is crushed, and the step S2
In Step 10, the water vapor adsorbing substance on the powder may be prepared and the two may be mixed. Further, these are molded (step S230) to complete the shift catalyst. As a molding method, as in the first embodiment, a method of crushing the mixture obtained in step S220 and then crushing it into pellets can be mentioned.

Based on the second embodiment as described above, a shift catalyst having the same effect as the shift catalyst according to the first embodiment can be obtained.

C. Third Embodiment: In the first embodiment, the active species are supported on the mixture of the auxiliary component and the water vapor adsorbing substance, but the active species may be supported only on the auxiliary component. FIG. 4 is a process diagram showing a method of manufacturing a shift catalyst according to the third embodiment of the present invention. In the present embodiment, first, an auxiliary component is prepared (step S300). As the auxiliary ingredients prepared here,
The same oxide as that of the first embodiment can be used. Next, this auxiliary component is immersed in a solution containing an active species, as in step S120 of FIG. 1 (step S310). Further, these are heated and dried (step S320) and baked (step S33).
0), a catalytic material having active species supported on auxiliary components is obtained.

Next, a water vapor adsorbing substance similar to that of the above-described embodiment is prepared (step S340). And
This water vapor adsorbing substance is mixed with the catalyst substance obtained in step S330 (step S350). further,
Such a mixture is molded in the same manner as the above-described embodiment (step S360) to complete the shift catalyst.

According to the shift catalyst according to the third embodiment, the active species are supported only on the auxiliary component and not on the water vapor adsorbing substance. A state of the shift catalyst manufactured according to the manufacturing process shown in FIG. 4 is schematically shown in FIG. When the shift reaction is carried out using such a catalyst, the water vapor in the gas is attracted to the water vapor adsorbing substance, so that the water vapor concentration around the active species on the auxiliary component existing in the vicinity thereof is increased, which causes the shift reaction. Would be promoted. Furthermore, when the above-mentioned noble metal is used as the active species and the above-mentioned oxide is used as the auxiliary component, the active species is supported only on the auxiliary component that enhances the activity of promoting the shift reaction. The catalytic performance of the shift reaction can be further enhanced.

D. Fourth Embodiment: In the above-described embodiments, a configuration in which the shift catalyst is formed into a pellet shape when molded is described, but it is also possible to use a shift catalyst having a different shape. FIG. 6 is a process diagram showing a method of manufacturing a shift catalyst according to the fourth embodiment of the present invention. In the present embodiment, first, a slurry of a water vapor adsorbing substance is prepared (step S400). As the water vapor adsorbing substance,
As mentioned above, various zeolites can be used,
The slurry is manufactured by adding a predetermined binder to the powdery water vapor adsorbing substance. It is preferable to use an oxide sol as the binder, because the heat resistance of the shift catalyst can be sufficiently ensured.

Next, the surface of the honeycomb is coated with this water vapor adsorbing substance slurry (step S41).
0). As the honeycomb used as the substrate for supporting the catalyst, a ceramic monolith such as cordierite may be used, or a metal honeycomb tube such as stainless steel may be used. The honeycomb coated with a slurry of water vapor adsorbent is dried and
It is subjected to the firing process (step S420).

Next, a slurry of catalytic material containing active species is prepared (step S430). For example, when a precious metal is used as the active species and the above-mentioned oxide is used as the auxiliary component, the catalyst substance is immersed in the precious metal solution for drying and firing to evaporate to dryness and ion exchange. It can be manufactured by carrying out. Alternatively, as shown in step S200 of the second embodiment, Cu-Z
The n catalyst and the Fe-Cr catalyst may be produced by a coprecipitation method or the like. By crushing such a catalyst substance and adding a binder such as an oxide sol, a catalyst substance slurry can be obtained. Next, the surface of the honeycomb dried and fired in step S420 is coated with this slurry (step S440), and the coated honeycomb is further dried and fired (step S450) to complete the shift catalyst. As a result, a shift catalyst having a lower layer provided with the water vapor adsorbing substance and an upper layer formed covering the lower layer and provided with the catalytic substance is obtained.

In the shift catalyst according to the fourth embodiment as described above, on the honeycomb, a water vapor adsorbing substance layer made of a water vapor adsorbing substance is formed on the honeycomb side (the substrate side supporting the catalyst) on the surface side. Has a layer of catalytic material containing active species. The state of the shift catalyst manufactured according to the manufacturing process shown in FIG. 6 is schematically shown in FIG. When the shift reaction is carried out using such a catalyst, the water vapor in the gas is attracted to the water vapor adsorbing substance layer, and the attracted water vapor is the active species in the catalyst substance layer formed on the water vapor adsorbing substance layer. Subjected to the shift reaction that proceeds above. Thus, it is considered that the shift reaction is promoted by promoting the supply of water vapor onto the active species.

Further, in the present embodiment, since the catalyst substance layer, which is the field of the shift reaction, is formed on the surface side (upper layer), carbon monoxide in the gas is used for the shift reaction which proceeds on the active species. In addition, the water vapor adsorbing substance layer does not prevent the release of hydrogen and carbon dioxide generated by the shift reaction into the gas. This can further improve the catalyst performance.

As described above, in the shift catalyst according to the fourth embodiment, the catalyst substance slurry containing the active species is prepared separately from the water vapor adsorbing substance, so that the gas for the active species is not generated during the shift reaction. The supply and discharge are prevented from being hindered by the water vapor adsorbing substance. On the other hand, even if a part of the active species is carried on the water vapor adsorbing substance, the effect of improving the catalytic activity can be obtained by using the water vapor adsorbing substance. For example, when a noble metal is used as the active species and the above-mentioned oxide is used as the auxiliary component, the water vapor adsorbing substance layer is formed as the lower layer and the auxiliary component layer is formed as the upper layer on the honeycomb. Such a honeycomb may be dipped in a noble metal solution to support the active species on the honeycomb. Even in such a case, the noble metal which is the active species is mainly supported on the oxide which is the auxiliary component.

Alternatively, when a layer in which the water vapor adsorbing substance, the auxiliary component and the active species are mixed is formed on the honeycomb, the effect of improving the catalyst performance can be obtained by providing the water vapor adsorbing substance. An example of a catalyst having a layer in which a water vapor adsorbing substance, an auxiliary component, and an active species are mixed is shown in FIG.
It shows in (B). When manufacturing such a shift catalyst, for example, instead of step S400 of FIG. 6, a slurry of a mixture of a catalyst substance containing an active species and a water vapor adsorbing substance may be produced. By coating a honeycomb with this slurry and performing drying and firing, it is possible to manufacture a honeycomb-shaped shift catalyst including a layer in which active species, a water vapor adsorbing substance, and an auxiliary component are mixed.

In each of the above-mentioned embodiments, various values can be selected for the ratio of the water vapor adsorbing substance.
For example, in step S110 of the first embodiment, the catalyst can be manufactured by mixing the auxiliary component and the same amount of the water vapor adsorbing substance. Alternatively, the second
In step S220 of the embodiment or step S350 of the third embodiment, the catalyst can be manufactured by mixing the catalyst substance and the same amount of the water vapor adsorbing substance. The amount of the water vapor adsorbing substance to be used may be determined so that the effect of promoting the shift reaction by attracting water vapor by the water vapor adsorbing substance is significantly obtained.

F. Device configuration: The shift catalyst shown in each of the above-described embodiments can be used in, for example, a fuel cell system. FIG. 8 is an explanatory diagram showing the configuration of a fuel cell system having a shift section including such a shift catalyst.

The fuel cell system shown in FIG. 8 includes a fuel cell 18 and a fuel gas supplied to the fuel cell 18. And a fuel reformer for generating the fuel. The fuel reforming device is a device that generates hydrogen by reforming a predetermined raw fuel, and has a reforming unit 10, a cooler 12, a shift unit 14, and a CO oxidation unit 16 as main constituent elements. The raw fuel may be appropriately selected from hydrocarbons such as natural gas and gasoline, alcohols such as methanol, ethers and aldehydes, and the like capable of generating hydrogen by a reforming reaction.

In the reforming section 10, these raw fuels are
Together with steam and air, it is subjected to a reaction called a steam reforming reaction or a partial oxidation reaction to generate a hydrogen-rich gas containing CO. The produced hydrogen-rich gas is
The carbon monoxide concentration is reduced by being supplied to the shift unit 14 and the CO oxidation unit 16. Here, the reforming unit 10, the shift unit 14, and the CO oxidation unit 16 each include a catalyst that promotes a reaction that proceeds inside, and the internal temperature is controlled so that the reaction temperature corresponds to the catalyst. For example, when gasoline or the like is used as the raw fuel, the reforming reaction is carried out at a temperature condition of about 900 ° C., while the shift reaction promoted by the shift catalyst is carried out at a temperature condition of about 200 to 300 ° C. Therefore, in the fuel cell system shown in FIG. 8, the hydrogen-rich gas generated in the reforming section 10 is
Prior to being supplied to the shift unit 14, the cooler 12 cools it.

The shift section 14 is internally provided with the shift catalyst of the above-described embodiment, receives hydrogen-rich gas supplied from the cooler 12 to advance the shift reaction, and changes the carbon monoxide concentration in the hydrogen-rich gas. Reduce. Here, the shift catalyst included in the shift portion 14 is formed in a pellet shape as shown in the first to third embodiments, and the shift portion 14 is formed.
It may be filled in the inside or may be housed in the shift portion 14 in a state where the honeycomb is coated as shown in the fourth embodiment.

The hydrogen-rich gas whose carbon monoxide concentration has been reduced by the shift portion 14 is supplied to the CO oxidation portion 16 to further reduce the carbon monoxide concentration. CO oxidation unit 16
In the above, a carbon monoxide selective oxidation reaction in which carbon monoxide is oxidized is preferentially carried out over hydrogen that is present in a larger amount. The hydrogen-rich gas whose carbon monoxide concentration has been sufficiently reduced in this way is supplied as a fuel gas to the anode side of the fuel cell 18 and is subjected to an electrochemical reaction. Air is supplied as an oxidizing gas to the cathode side of the fuel cell 18.

In such a fuel cell system, the shift section 14 includes the shift catalyst of the above-mentioned embodiment, and the carbon monoxide concentration in the hydrogen rich gas can be further lowered. Further, since the activity of promoting the shift reaction is high, the shift unit 14 can be made smaller, and the entire device can be made smaller.

[0043]

EXAMPLES (A) Examples 1 to 6 and Comparative Examples 1 to 3: The catalysts of Examples 1 to 6 and the catalysts of Comparative Examples 1 to 3 shown in FIG. 9 were produced and their catalytic performances were compared. In addition, Examples 1 to 6
And the catalysts of Comparative Examples 1 to 3 were molded into pellets.

(A-1) Example 1: The catalyst of Example 1 is
Platinum as an active species and titania (Ti as an auxiliary component)
O ₂ ) was used as the catalyst material. As the water vapor adsorbing substance, ZSM-5, which is one type of zeolite, was used. Moreover, the catalyst of Example 1 was manufactured based on the manufacturing method (FIG. 1) described in the first embodiment.

When the catalyst of Example 1 was manufactured according to the manufacturing process shown in FIG. 1, 10 g of titania powder and 10 g of ZSM-5 powder were prepared in step S100. In step S120, the mixed powder obtained by mixing the above two kinds of equal amounts of powder was immersed in a platinum nitrate solution. The platinum nitrate solution used contains an amount of platinum salt such that the amount of supported platinum is 5% by weight. The amount of platinum carried means the ratio of "platinum weight" to "the total amount of the weight of titania, the weight of ZSM-5 and the weight of platinum". The above-mentioned mixed powder is immersed in a platinum nitrate solution prepared so that the platinum amount in platinum nitrate contained in the platinum nitrate solution becomes equal to the platinum amount when the platinum loading amount becomes 5% by weight. The treatment of immersing the mixed powder in the platinum nitrate solution prepared as described above is performed at room temperature with stirring.
I went on time.

In step S130, the platinum nitrate solution in which the mixed powder was dipped was heated to 200 ° C. to evaporate the water content and dried at 120 ° C. overnight. Step S
In 140, it baked at 400 degreeC for 2 hours. In the molding step of step S150, the product calcined in step S140 was crushed after compression, and the crushed product was further sieved to obtain a pellet-shaped shift catalyst having a particle diameter of 1 mm to 3 mm. In this way, the catalyst of Example 1 in the form of pellets having a platinum loading of about 5% by weight was produced. As shown in FIG. 2, the catalyst of Example 1 contained titania as an auxiliary component and ZSM- as a water vapor adsorbing substance.
Both of them have a shape in which platinum which is an active species is carried.

(A-2) Example 2: The catalyst of Example 2 is
It was produced in the same manner as in the catalyst of Example 1 except that zeolite β was used instead of ZSM-5 as the water vapor adsorbing substance. Therefore, as shown in FIG. 2, the catalyst of Example 2 has a shape in which platinum as an active species is supported on both titania as an auxiliary component and zeolite β as a water vapor adsorbing substance. .

(A-3) Example 3: The catalyst of Example 3 is
A catalytic material consisting of platinum as an active species and titania as an auxiliary component was used. Further, as the water vapor adsorbing substance,
ZSM-5, which is one type of zeolite, was used. Moreover, the catalyst of Example 3 was manufactured based on the manufacturing method (FIG. 4) described in the third embodiment.

When the catalyst of Example 3 was manufactured according to the manufacturing process shown in FIG. 4, titania powder was prepared in step S300, and this titania powder was immersed in a platinum nitrate solution in step S310. In this step S310, the platinum nitrate solution used is
It contains an amount of platinum salt such that the amount of supported platinum is 10% by weight. Here, the amount of platinum supported means the ratio of “platinum weight” to “total amount of titania weight and platinum weight”. In step S310, the titania powder is immersed in such a platinum nitrate solution and treated for 3 hours with stirring at room temperature, whereby 10% by weight of the titania on the titania is obtained by the ion exchange method.
Supported platinum.

The heating / drying process in step S320 and the firing process in step S330 are the same as those in step S130.
And it performed like step S140. Step S
In 340, ZSM-5 powder is prepared, and step S33 is performed.
An equal amount was mixed with crushed platinum-supported titania that had been calcined at 0. The molding in step S360 was performed in the same manner as in step S150. In this manner, a pellet-form catalyst of Example 3 having a platinum loading amount (ratio of platinum weight to total catalyst weight) of about 5% by weight was produced. As shown in FIG. 5, in the catalyst of Example 3, platinum which is an active species is supported on titania which is an auxiliary component, but platinum is not supported on ZSM-5 which is a water vapor adsorbing substance. It has a shape.

(A-4) Example 4: The catalyst of Example 4 is
It was produced in the same manner as the catalyst of Example 3 except that zeolite β was used instead of ZSM-5 as the water vapor adsorbing substance. Therefore, in the catalyst of Example 4, platinum, which is an active species, is supported on titania, which is an auxiliary component, as shown in FIG.
The shape is such that platinum is not supported on the top.

(A-5) Example 5: The catalyst of Example 5 is
A Cu-Zn catalyst was used as a catalyst substance. Further, ZSM-5 was used as the water vapor adsorbing substance. Moreover, the catalyst of Example 5 was manufactured based on the manufacturing method (FIG. 3) described in the second embodiment.

In step S210, ZSM-5 powder is prepared, and in step S220, the catalyst substance and ZSM-5 are prepared.
-5 powder was mixed in equal amounts. The molding process of step S230 was performed in the same manner as step S150 of FIG. 1 described above. As a result, Cu-Zn, which is the catalytic substance,
A catalyst of Example 5 was obtained in the form of pellets in which the catalyst and ZSM-5 were mixed almost uniformly.

(A-6) Example 6: The catalyst of Example 6 is
It was prepared in the same manner as the catalyst of Example 5 except that the Fe-Cr catalyst was used as the catalyst material instead of the Cu-Zn catalyst. As a result, the Fe--Cr catalyst and Z
Example 6 in the form of a pellet in which SM-5 is mixed substantially uniformly
The catalyst was obtained.

(A-7) Comparative Example 1: The catalyst of Comparative Example 1 is
It is a comparative example with respect to the catalysts of Examples 1 to 4.
The catalyst of Comparative Example 1 is provided with a catalytic substance composed of platinum as an active species and titania as an auxiliary component, but unlike the catalysts of the above-mentioned examples, it does not have a water vapor adsorbing substance. The catalyst of Comparative Example 1 was produced in the same manner as the catalyst of Example 1 except that only the auxiliary component was prepared in step S100 of FIG. 1 instead of the auxiliary component and the water vapor adsorbing substance. When manufacturing the catalyst of Comparative Example 1, 20 g of titania was prepared in the process corresponding to step S100. Therefore, the catalyst of Comparative Example 1 has a shape in which platinum, which is an active species, is supported on titania, which is an auxiliary component (not shown).

(A-8) Comparative Example 2: The catalyst of Comparative Example 2 is
6 is a comparative example for the catalyst of Example 5. The catalyst of Comparative Example 2 was formed into a catalyst material without performing steps S210 and S220 of FIG. Therefore, the catalyst of Comparative Example 2 does not have a water vapor adsorbing substance, and is formed into a pellet shape only by the Cu—Zn catalyst which is a catalytic substance.

(A-9) Comparative Example 3: The catalyst of Comparative Example 3 was
6 is a comparative example for the catalyst of Example 6. The catalyst of Comparative Example 3 was a Fe—C catalyst material instead of the Cu—Zn catalyst.
The catalyst was prepared by the same method as the catalyst of Comparative Example 2 except that the r catalyst was used. Therefore, the catalyst of Comparative Example 3 does not have a water vapor adsorbing substance, and is Fe- which is a catalytic substance.
It is formed in a pellet shape only with the Cr catalyst.

(A-10) Performance Evaluation of Catalysts of Examples 1 to 6: The shift catalysts of Examples 1 to 6 and the shift catalysts of Comparative Examples 1 to 3 were used to compare the performance of promoting the shift reaction. The results obtained are shown in FIG. FIG. 9 shows the result of measuring the CO conversion rate in order to compare the performance of the shift catalyst. CO conversion rate (%) means CO _{2 due to} shift reaction.
Is expressed as the molar ratio of the CO and the CO before the reaction.

When measuring the CO conversion, a reactor of the same size was prepared for each catalyst, and 2 g each of the catalyst of the above-mentioned example and the catalyst of the comparative example were packed in each reactor. did. At this time, prior to measuring the CO conversion rate,
Each catalyst was pretreated for reduction. After performing the firing process like step S140 shown in FIG. 1, the metal components such as active species included in the shift catalyst are in an oxidized state. By carrying out a pretreatment for reduction prior to using such a catalyst for promoting the shift reaction, the activity as a shift catalyst can be sufficiently enhanced. The conditions of the pretreatment were as follows: the reactor equipped with each catalyst was heated to 350 ° C.
A gas containing 100% of hydrogen was supplied to perform treatment in such a hydrogen-rich atmosphere for 30 minutes.

After the above pretreatment, a predetermined test gas was supplied to the reactor equipped with each catalyst, the amount of carbon monoxide in the gas discharged from the reactor was measured, and the CO conversion rate was calculated. . The conditions for supplying the test gas to measure the CO conversion are as follows. The composition of the following test gas used when measuring the CO conversion was set based on the composition of the hydrogen-rich gas obtained by performing the reforming reaction using gasoline as a raw fuel. Composition of test gas (dry state) ... N ₂ = 38.16%,
H ₂ = 39.53%, CO = 9.94%, CO ₂ = 12.
37%; amount of water vapor (molar ratio) ... H ₂ O / CO = 3.05; total gas flow rate = 2100 cc / min; inlet gas temperature (temperature of test gas supplied to reaction tank filled with each catalyst) ... 240 ° C. ;

As shown in FIG. 9, the shift catalysts of Examples 1 to 6 exhibited higher CO conversion rates than the corresponding catalysts of Comparative Examples 1 to 3. In addition, among the examples, Examples 3 and 4 in which platinum was supported only on titania
Showed a higher CO conversion rate as compared with Examples 1 and 2 in which platinum was supported on both titania and zeolite.

(B) Examples 7 to 9 and Comparative Examples 4 and 5:
Catalysts of Examples 7 to 9 shown in FIG. 10, and Comparative Examples 4 and 5
Catalysts were produced and their catalytic performances were compared. In addition, Example 7
.About.9 and the catalysts of Comparative Examples 4 and 5 were manufactured by using a honeycomb.

(B-1) Example 7: The catalyst of Example 7 is
A catalytic material consisting of platinum as an active species and titania as an auxiliary component was used. Further, as the water vapor adsorbing substance,
ZSM-5 was used. Moreover, the catalyst of Example 7 was manufactured based on the manufacturing method (FIG. 6) described in the fourth embodiment. Here, a honeycomb made of cordierite was used as the base material of the catalyst. These honeycombs are columnar with a cross-sectional diameter of 30 mm and a length of 50 mm.

When the catalyst of Example 7 is manufactured according to the manufacturing process shown in FIG. 6, ZS is performed in step S400.
A slurry of M-5 was prepared. Further, in step S410, at a rate of 120 g per liter of honeycomb volume,
The honeycomb was coated with this slurry. Step S42
In 0 and step S450, drying was performed at 120 ° C. for 5 hours and firing was performed at 350 ° C. for 2 hours. In step 430, the titania powder was dipped in platinum nitrate to prepare a catalyst substance produced so that the amount of platinum supported on the titania was 10% by weight, and this was slurried. In addition, in step S440, 12
The honeycomb was coated with a catalyst substance slurry (platinum-supported titania slurry) at a rate of 0 g. Therefore, the catalyst of Example 7 was formed on a honeycomb substrate, as shown in FIG. 7A, with a lower layer (water vapor adsorbing substance layer) containing ZSM-5 and a platinum-supported lower layer. It has a shape including an upper layer (catalyst substance layer) containing titania.

(B-2) Example 8: The catalyst of Example 8 is
In step S400 of FIG. 6, as the water vapor adsorbent slurry, zeolite β is used instead of ZSM-5 slurry.
Was prepared in the same manner as the catalyst of Example 7, except that the slurry of Example No. 1 was used. Therefore, the catalyst of Example 8 was formed on the honeycomb substrate as shown in FIG. 7 (A) to form the lower layer (water vapor adsorbing substance layer) containing zeolite β and the platinum-supporting titania formed so as to cover the lower layer. Upper layer containing (catalyst material layer)
It has a shape with and.

(B-3) Example 9: The catalyst of Example 9 is
In step S430 of FIG. 6, the catalyst substance slurry was produced in the same manner as the catalyst of Example 7, except that the slurry of the Cu-Zn catalyst was used as the catalyst substance slurry instead of the platinum-supported titania slurry. Therefore, the catalyst of Example 9 is shown in FIG.
As shown in FIG. 7, a honeycomb was provided with a lower layer containing ZSM-5 (water vapor adsorbing substance layer) and an upper layer covering the same and containing a Cu—Zn catalyst (catalyst substance layer). It has a shape.

(B-4) Comparative Example 4: The catalyst of Comparative Example 4 was
It is a comparative example with respect to Examples 7 and 8. The catalyst of Comparative Example 4 was provided with a catalyst substance layer made of platinum-supported titania on a honeycomb, but unlike the catalysts of the above-mentioned examples, it did not have a water vapor adsorbing substance. Such a catalyst of Comparative Example 4 is obtained by using the method for producing the shift catalyst shown in FIG.
Without performing steps corresponding to steps S400 to S420, steps S430 to S4
It was manufactured by performing only the steps corresponding to 50. At this time, in step S430, the catalyst substance was prepared by immersing the titania powder in platinum nitrate so that the amount of platinum supported on the titania was 5% by weight. In addition, in step S440, 240
Honeycomb was coated with this slurry at a rate of g. As a result, the catalyst of Comparative Example 4 had a shape in which a layer having substantially the same amount of active species (platinum) as the catalyst of Example 7 or 8 had in the upper layer (catalyst material layer) was formed on the honeycomb. (Not shown).

(B-5) Comparative Example 5: The catalyst of Comparative Example 5 was
9 is a comparative example with respect to Example 9. The catalyst of Comparative Example 5 was manufactured by the same method as that of the catalyst of Comparative Example 4 above, except that a Cu—Zn catalyst was used as the catalyst substance instead of the platinum-supported titania. Therefore, the catalyst of Comparative Example 5 did not form the water vapor adsorbing substance layer on the honeycomb, and the Cu-
It has a shape having only a catalyst material layer including a Zn catalyst.

(B-6) Performance Evaluation of Catalysts of Examples 7 to 9: The shift catalysts of Examples 7 to 9 and the shift catalysts of Comparative Examples 4 and 5 were used to compare the performance of promoting the shift reaction. The results obtained are shown in FIG. Similar to FIG. 9, FIG. 10 shows the result of measuring the CO conversion rate as the catalyst performance.

Prior to the measurement of the CO conversion, each honeycomb catalyst manufactured as described above was subjected to the above-mentioned pretreatment. The conditions for the pretreatment are the same as in the previous embodiment.

After the above pretreatment, a predetermined test gas was supplied to the reactor equipped with each catalyst, the amount of carbon monoxide in the gas discharged from the reactor was measured, and the CO conversion rate was calculated. . The conditions for supplying the test gas to measure the CO conversion are as follows. The composition of the following test gas used when measuring the CO conversion was set based on the composition of the hydrogen-rich gas obtained by performing the reforming reaction using gasoline as a raw fuel. Composition of test gas (dry state) ... N ₂ = 38.16%,
H ₂ = 39.53%, CO = 9.94%, CO ₂ = 12.
37%; amount of water vapor (molar ratio) ... H ₂ O / CO = 3.05; total gas flow rate = 2100 cc / min; space velocity (dry state) = 3600 h ^-1 gas temperature (in the reaction tank filled with each catalyst) Temperature of supplied test gas) ... 240 ° C .;

As shown in FIG. 10, the shift catalysts of Examples 7 to 9 showed higher CO conversion rates than the corresponding catalysts of Comparative Examples 4 and 5.

[Brief description of drawings]

FIG. 1 is a process diagram showing a method of manufacturing a shift catalyst according to a first embodiment.

FIG. 2 is an explanatory view schematically showing a state of a shift catalyst according to the first embodiment.

FIG. 3 is a process chart showing a method of manufacturing a shift catalyst according to a second embodiment.

FIG. 4 is a process chart showing a method of manufacturing a shift catalyst according to a third embodiment.

FIG. 5 is an explanatory diagram schematically showing a state of a shift catalyst according to a third embodiment.

FIG. 6 is a process chart showing a method of manufacturing a shift catalyst according to a fourth embodiment.

FIG. 7 is an explanatory view schematically showing a state of a shift catalyst in which a water vapor adsorbing substance is mixed.

FIG. 8 is an explanatory diagram showing a configuration of a fuel cell system having a shift section including a shift catalyst.

FIG. 9 is an explanatory diagram showing the conditions relating to the catalyst of each example and the catalyst of the comparative example, and the results of measuring the CO conversion rate.

FIG. 10 is an explanatory diagram showing the conditions relating to the catalyst of each example and the catalyst of the comparative example, and the results of measuring the CO conversion rate.

[Explanation of symbols]

12 ... Cooler 14 ... shift part 16 ... CO oxidation part 18 ... Fuel cell

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01J 37/02 B01J 37/02 301L C01B 3/16 C01B 3/16 3/48 3/48 H01M 8/06 H01M 8 / 06 G F-term (reference) 4G040 CA03 CA04 EB32 4G069 AA03 AA08 BA04A BA04B BA07A BA07B BB04B BC31A BC31B BC32A BC33A BC35A BC35B BC58A BC58B BC66A BC66B BC69A BC75A BC75B CC26 DA06 EA02X EA19 EE08 FA01 FA03 FB07 FB14 FB23 FB26 FB64 ZA11B ZA19B 5H027 AA06 BA01 BA17

Claims (12)

[Claims] 1. A shift catalyst having an activity of promoting a shift reaction for producing hydrogen and carbon dioxide from water and carbon monoxide, the catalyst material containing an active species having an activity of promoting the shift reaction, A shift catalyst comprising a water vapor adsorbing substance capable of adsorbing water vapor. 2. The shift catalyst according to claim 1, wherein the catalyst substance contains a noble metal that functions as the active species and an oxide that supports the noble metal. 3. The shift catalyst according to claim 2, wherein the active species does not substantially exist on the water vapor adsorbing substance but exists on the oxide. 4. The shift catalyst according to claim 2, wherein the noble metal is platinum and the oxide is titania. 5. The shift catalyst according to claim 1, wherein the catalyst substance is a mixture of a plurality of components containing a metal serving as the active species. 6. The shift catalyst according to claim 5, wherein the catalyst material is a copper-zinc catalyst or an iron-chromium catalyst. 7. The shift catalyst according to claim 1, wherein the water vapor adsorbing substance is zeolite. 8. The shift catalyst according to claim 1, wherein the first layer is formed on a predetermined base material and contains the water vapor adsorbing substance, and the shift layer is formed on the first layer. And a second layer containing said catalytic material. 9. A method for producing a shift catalyst having an activity of promoting a shift reaction for producing hydrogen and carbon dioxide from water and carbon monoxide, which comprises (a) an active species having an activity of promoting the shift reaction. A step of preparing a contained catalyst substance, a step of (b) preparing a water vapor adsorbent substance capable of adsorbing water vapor, (c) a step of mixing the catalyst substance and the water vapor adsorbent substance, and (d) ) A step of producing a shift catalyst, comprising the step of molding a mixture of the catalyst substance and the water vapor adsorbing substance obtained in the step (c). 10. The method for producing a shift catalyst according to claim 9, wherein in the step (a), a noble metal serving as the active species is supported on a predetermined oxide to form a noble metal-supported oxide. A method for producing a shift catalyst, which comprises the step of producing the catalyst substance containing the noble metal-supported oxide. 11. A method for producing a shift catalyst having an activity of promoting a shift reaction for producing hydrogen and carbon dioxide from water and carbon monoxide, comprising: (a) an active species having an activity of promoting the shift reaction. A step of preparing an auxiliary component having a function of retaining the active species and a water vapor adsorbing substance capable of adsorbing water vapor; and (b) a step of mixing the auxiliary component and the water vapor adsorbing substance. , (C) the above (b)
Supporting the active species on the mixture of the auxiliary component and the water vapor adsorbing substance obtained in the step, and (d)
A step of molding the mixture supporting the active species in the step (c). 12. A method for producing a shift catalyst having an activity of promoting a shift reaction for producing hydrogen and carbon dioxide from water and carbon monoxide, which comprises (a) an active species having an activity of promoting the shift reaction. A containing catalyst substance, a water vapor adsorbing substance capable of adsorbing water vapor, and a substrate having a predetermined shape,
And (b) forming a water vapor adsorption layer comprising the water vapor adsorbing substance on the substrate,
(C) A step of forming a catalyst substance layer including the catalyst substance on the water vapor adsorption layer, the method for producing a shift catalyst.