JP2003236380A - Shift catalyst and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique to improve the activity of shift reaction. <P>SOLUTION: The shift catalyst is manufactured in steps of: first mixing TiO<SB>2</SB>with an additive oxide containing at least one of CeO<SB>2</SB>and WO<SB>3</SB>(S100); adding a binder to the obtained mixture powder to produce a slurry (S110); coating a specified catalyst base body with the produced slurry (S120); drying and calcining (S130); further depositing platinum on the surface (S140); and drying and calcining (S150) to obtain the shift catalyst. The catalytic performance can be improved by depositing platinum on the TiO<SB>2</SB>containing the additive oxide. <P>COPYRIGHT: (C)2003,JPO

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. 2-69301 discloses a catalyst in which platinum and / or palladium is supported on an alumina base material.

[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.

The Cu-based catalyst has a space velocity SV (Space
It has a characteristic that the CO reduction rate sharply decreases as the Velocity) increases. Therefore, C
In order to treat more CO with the u-based catalyst,
It was necessary to increase the catalyst volume, that is, upsize the reactor. Further, the above noble metal-based catalyst has a higher heat resistance temperature than the Cu-based catalyst, and even when the space velocity SV increases, CO
There is little decrease in the reduction rate. However, the noble metal catalyst sometimes has an insufficient CO reduction rate itself.
Therefore, a shift catalyst having higher activity for 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.

[0008]

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 for producing hydrogen and carbon dioxide from water and carbon monoxide. A method of manufacturing, comprising: (a) titania (TiO) containing at least one of an oxide of cerium (Ce) and an oxide of tungsten (W).
_The gist of the present invention is to include a step of producing a carrier composed of ₂ ) and (b) a step of supporting platinum (Pt) on the carrier.

According to such a method for producing a shift catalyst, it is possible to obtain a shift catalyst having a higher activity of promoting the shift reaction. In particular, it is possible to produce a shift catalyst that exhibits sufficient catalytic activity even in a lower temperature range.

In the method for producing a shift catalyst according to the present invention, the step (a) includes (a-1) a step of preparing a mixture of the titania and the oxide, and (a-2)
And a step of forming the carrier by using the mixture.

In the shift catalyst manufacturing method of the present invention as described above, the step (a-2) is a step of adding a predetermined binder to the mixture to form a slurry and supporting the slurry on a predetermined substrate. It may be included.

In addition to the structure in which the above mixture is supported on a base material having a predetermined shape, the above mixture or a platinum-supported mixture is molded into a predetermined shape without using a base material. Also good.

The method for producing a shift catalyst of the present invention further comprises the step of (c) adding at least one element selected from alkali metal elements, alkaline earth metal elements and rare earth elements to the carrier. Also good.

This makes it possible to obtain a shift catalyst having a higher activity for promoting the shift reaction. Further, it is possible to produce a shift catalyst exhibiting sufficient catalytic activity even in a lower temperature range. The step (c) of adding at least one element may be performed before or after the platinum is loaded on the carrier.

The present invention can be realized in various forms other than those described above, and can be realized, for example, in the form of a shift catalyst, a carbon monoxide concentration reducing unit including the shift catalyst, a fuel cell system, or the like. Is.

[0016]

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, titania and the added oxide are mixed (step S10).
0). At the time of mixing, titania and the added oxide are prepared in the form of powder, and these powders are mixed.
As the additional oxide prepared in this step S100,
Cerium oxide (CeO ₂ ) and / or tungsten oxide (WO ₃ ) are used. At that time, the mixing ratio of both is preferably 1 to 50% by weight, more preferably 1 to 15% by weight, based on the total amount of the mixed oxide powder composed of titania and the additional oxide. desirable.

When preparing the mixed powder of titania and the added oxide powder in step 100, a manufacturing method other than mixing the powders prepared separately in advance as described above may be used. For example, titanium hydroxide (T
When a titania powder is prepared by firing an iOH) gel, it is also possible to prepare a mixed powder of titania and cerium oxide by previously mixing a gel hydroxide containing cerium with the titanium hydroxide gel. is there.

Next, a binder is added to the mixed powder obtained in step S100 to prepare a slurry (step S).
110). Examples of the binder used for producing the slurry include titania (TiO ₂ ) sol and ceria (Ce).
O ₂ ) sol, zirconia (ZrO ₂ ) sol, alumina (Al ₂ O ₃ ) sol, silica (SiO ₂ ) sol and the like can be used. Such a metal oxide sol has sufficient heat resistance and is desirable as a binder. In addition,
In the step S100, a mixed powder of titania and the added oxide was prepared, but this mixed powder was sufficiently prepared to prepare a slurry that could be carried on a predetermined base material when the binder was used. Any fine particles may be used.

Next, the slurry prepared in step S110 is applied onto a predetermined catalyst substrate (step S12).
0). As the predetermined catalyst base material, for example, a ceramic honeycomb monolith such as cordierite can be used. Alternatively, a honeycomb tube made of metal such as stainless steel may be used. Alternatively, pellets formed of a metal oxide such as alumina can be used. After coating with the slurry as described above, the catalyst substrate is once dried and calcined (step S130).

After that, platinum is supported on the dried and calcined catalyst substrate (step S140). Platinum is supported by immersing the catalyst substrate in a platinum salt solution. As the platinum salt solution, for example, a water-soluble solution such as a platinum nitrate solution can be used. By immersing the catalyst base material in a platinum salt solution, platinum can be supported on the oxide (titania and added oxide) on the catalyst base material by an ion exchange method or an impregnation method.
In step S140, the catalyst base material carrying platinum is
Further, the shift catalyst is completed by drying and firing (step S150).

As described above, in the shift catalyst, titania, which is a carrier for supporting platinum that is an active species, is previously mixed with cerium oxide (CeO ₂ ) and tungsten oxide (WO).
By mixing at least one of ( ₃ ) and ( ₃ ), the activity of promoting the shift reaction can be improved. Particularly, even at a lower temperature (for example, a temperature range of 350 ° C. or lower), it becomes possible to obtain sufficient activity that promotes the shift reaction.

As described above, according to the present embodiment, the effect of improving the activity of promoting the shift reaction is obtained, so that it is sufficient to reduce the amount of platinum which is the catalyst active material supported on the shift catalyst. It becomes possible to obtain catalytic activity. As a result, the cost for manufacturing the catalyst can be reduced.

In order for the catalyst to exhibit sufficient activity,
It is necessary to provide a sufficient amount of catalyst active material. However, when platinum is used as the catalyst active material, the interaction between the platinum and the catalyst carrier such as titania (SMS
It is known that I) occurs. When the shift reaction is carried out using the catalyst, Pt comes to cover the catalyst carrier component due to the SMSI, the active sites are reduced, and the catalytic activity may be lowered. By being able to reduce the amount of platinum that is the catalyst active material as described above,
It is possible to further suppress the SMSI generated between the platinum and the catalyst carrier and further secure the catalytic activity.

B. Second Embodiment: FIG. 2 is a process diagram showing a method for manufacturing a shift catalyst according to a second embodiment of the present invention. The shift catalyst according to the second embodiment is different from the shift catalyst according to the first embodiment,
No catalyst substrate is used. In the present embodiment, first, similarly to step S100 of the first embodiment, titania and the additive oxide are mixed (step S200) to prepare a mixed powder. The added oxide and the mixed amount of the added oxide used are the same as in the first embodiment.

Next, platinum is supported on the mixed powder (step S210). The platinum is supported by immersing the mixed powder in the same platinum salt solution as that used in step S140 of the first embodiment. When platinum is supported on the mixed powder, it is further dried and fired (step S220). Then, the fired platinum-supported mixed powder is molded into a predetermined shape (step S23).
0), complete the shift catalyst. As a method of molding the fired platinum-supported mixed powder, there is, for example, a method of compressing the platinum-supported mixed powder and further pulverizing it to form a pellet.

[0026] Thus, CeO ₂ and WO ₃ were previously added to the titania, which is the main component of the carrier supporting the platinum, which is the active species.
Even if the shift catalyst in which at least one of the above is mixed is molded without using the catalyst base material, the same effect as that of the first embodiment can be obtained.

C. Third Embodiment: FIG. 3 is a process diagram showing a method of manufacturing a shift catalyst according to a third embodiment of the present invention. In the third embodiment, step S3
00 to step S350, steps S100 to S1 in the first embodiment shown in FIG.
Perform steps similar to 50. As a result, a layer of a carrier containing titania and an added oxide is formed on a predetermined catalyst substrate, and platinum is supported on the layer of the carrier, which is similar to the catalyst of the first embodiment. Is obtained.

Next, in this embodiment, the catalyst substrate having the carrier layer supporting platinum is immersed in the solution containing the salt of the additional element (step S360). Here, the additive element is composed of at least one element selected from alkali metal elements, alkaline earth metal elements, and rare earth elements. As the alkali metal element, lithium (Li), sodium (Na), potassium (K), rubidium (R
b) and cesium (Cs) can be mentioned. Examples of the alkaline earth metal element include magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). As a rare earth element,
For example, lanthanum (La), yttrium (Y), cerium (Ce), praseodymium (Pr), etc. can be mentioned.

By dipping the catalyst substrate having the carrier layer carrying platinum as described above in the solution containing the salt of the additive element, the carrier layer can further contain the additive element. When the catalyst base material is immersed in the solution of the salt of the additional element, the water absorption amount of the catalyst base material having the support layer supporting platinum may be examined in advance. Then, a solution of the salt of the additional element is prepared so that the concentration of the desired element of the additional element is contained in the solution of the amount absorbed. By further calcining and drying the catalyst base material dipped in the salt solution of the additional element (step S370), the additional element impregnated in the carrier layer can be supported on the carrier layer.
Complete the shift catalyst.

As described above, according to the third embodiment,
In titania, which is a carrier that supports platinum, which is an active species,
By mixing at least one of CeO ₂ and WO _{3 in} advance, the same effect as that of the first and second embodiments can be obtained. Furthermore, in a carrier layer comprising titania and an added oxide, by further containing the above-mentioned additional element, the activity of promoting the shift reaction is further improved, and particularly at a lower temperature (for example, a temperature range of 350 ° C. or lower). The catalytic activity can be further improved. One of the causes of such improvement in catalytic activity is that the addition of the above-mentioned additional element further enhances the property of drawing water (steam) into the shift catalyst and promotes the shift reaction. Is considered to be.

In addition, in the step of manufacturing the shift catalyst shown in FIG. 3, after the platinum was supported on the carrier layer, the additional element was further added. However, after the additive element is first added to the carrier layer, It is also possible to support platinum. That is, the steps S360 and S370 may be performed before the steps S340 and S350.

D. Fourth Embodiment: FIG. 4 is a process diagram showing a method of manufacturing a shift catalyst according to a fourth embodiment of the present invention. The shift catalyst according to the fourth embodiment is provided with an additive element in the carrier layer similarly to the shift catalyst according to the third embodiment, but unlike the shift catalyst according to the third embodiment, a catalyst base material is used. Not used. In the present embodiment, first, step S300 of the third embodiment.
Similarly, the titania and the additive oxide are mixed to prepare a mixed powder (step S400). The added oxide and the amount of the added oxide used are the same as those in the above-described embodiments.

Next, platinum is supported on the mixed powder (step S410), and this is dried and fired (step S420). The steps S410 and S420 are the same as the steps S210 and S220 in the second embodiment. Next, the calcined platinum-supported mixed powder is immersed in a solution containing a salt of an additional element. This step S4
24 is a process similar to step S360 in the third embodiment, and the additive element to be used can be selected from the above-mentioned alkali metal element, alkaline earth metal element, and rare earth element. When the additional element is further contained in this way, it is dried and fired (step S42).
6) Molding (step S430) to complete the shift catalyst. In the process of step S430, for example, the pellet-shaped molding may be performed similarly to the process of step S230 of FIG.

As described above, the shift catalyst prepared by previously mixing at least one of CeO ₂ and WO ₃ with titania, which is a carrier for supporting platinum as an active species, and further adding the above-mentioned additional element to the catalyst Even if molding is performed without using a substrate, the same effect as that of the third embodiment can be obtained. In the method of manufacturing the shift catalyst shown in FIG. 4, the step of adding the additive element to the mixed powder is performed first.
The step of supporting platinum may be performed later.

E. Device configuration: The shift catalyst shown in each of the above-described embodiments can be used in, for example, a fuel cell system. FIG. 5 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. 5 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. 5, 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 the supply of hydrogen-rich gas from the cooler 12 to advance the shift reaction, and changes the carbon monoxide concentration in the hydrogen-rich gas. Reduce.

The hydrogen-rich gas whose carbon monoxide concentration has been reduced by the shift section 14 is supplied to the CO oxidation section 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.

[0041]

EXAMPLES (A) Examples (1) and (2) and Comparative Examples (1) to (7): Catalysts of Examples (1) and (2) shown in FIG. 6 and Comparative Examples (1) to (7) The catalyst of (7) was manufactured and the catalyst performance was compared.

(A-1) Example (1): The catalyst of Example (1) was produced based on the production method (FIG. 1) shown in the above-described first embodiment. Using the catalyst of Example (1),
When manufacturing according to the manufacturing process shown in FIG. 1, cerium oxide (CeO ₂ ) powder was used as the additive oxide powder in step S100. The CeO ₂ powder was mixed with the TiO ₂ powder in an amount such that the proportion of CeO ₂ in the mixed powder obtained in step S100 was 4% by weight. In step S110, titania sol was mixed with the mixed powder to prepare a slurry.

In step S120, as the catalyst base material,
A honeycomb monolith made of cordierite was used. This monolith has a cross-sectional diameter of 45 mm and a length of 75 mm.
It has a cylindrical shape. The monolith was coated on the monolith at a rate of 120 g (weight after drying) per liter of the monolith, using the slurry prepared in step S110. In step S130, drying was performed at 120 ° C. for 24 hours and firing was performed at 350 ° C. for 2 hours.

In step S140, platinum (Pt) was supported by the ion exchange method using a platinum nitrate solution. The amount of Pt supported was 1.2 g per liter of monolith volume. Then, in step S150, it was dried at 120 ° C. for 24 hours and calcined at 350 ° C. for 2 hours to complete the catalyst of Example (1).

(A-2) Example (2): The catalyst of Example (2) is the same as the catalyst of Example (2) except that tungsten oxide (WO ₃ ) powder is used instead of CeO ₂ powder in the step S100. It was produced in the same manner as the catalyst of Example (1) above. The amount of WO ₃ powder used in step S100 is the same as the WO in the mixed powder obtained in step S100.
_{The amount of 3} was 4% by weight.

(A-3) Comparative Example (1): As a comparative example for the catalysts of the above-mentioned Examples (1) and (2), the catalyst of Comparative Example (1) was produced. The catalyst of this comparative example (1) is
In the process of step S100, the same as the catalyst of the above-mentioned Example (1) except that a TiO ₂ powder having no added oxide was prepared instead of preparing a mixed powder of the TiO ₂ powder and the added oxide powder. Manufactured.

(A-4) Comparative Examples (2) to (6): Further, as Comparative Examples to the catalysts of Examples (1) and (2), the catalysts of Comparative Examples (2) to (6) were produced. did. The catalysts of Comparative Examples (2) to (6) were used as CeO ₂ powder or W in comparison with TiO ₂ powder in the process of step S100.
The catalyst was produced in the same manner as the catalyst of Example (1) above, except that an oxide powder other than O ₃ powder was used. The catalyst of Comparative Example (2) is aluminum oxide (Al ₂ O ₃ ) powder, the catalyst of Comparative Example (3) is silicon oxide (SiO ₂ ) powder, and the catalyst of Comparative Example (4) is diphosphorus trioxide (P). ₂ O ₃ ) powder was used, the catalyst of Comparative Example (5) was diiron trioxide (Fe ₂ O ₃ ) powder, and the catalyst of Comparative Example (6) was nickel oxide (NiO ₂ ) powder. The amount of the oxide powder used was an amount such that the ratio of the oxide powder in the mixed powder obtained in step S100 was 4% by weight, as in the above example.

(A-5) Comparative Example (7): Further, a catalyst of Comparative Example (7) was produced. The catalyst of Comparative Example (7) contained TiO 2 as a catalytically active component that acts to promote the shift reaction.
Instead of using a platinum-supported oxide containing ₂ CuO / ZnO / Al ₂ O ₃ catalyst was used. Specifically, on the same monolith as in the above embodiment, Toyo CC
MDC4 ™ from I was coated at a rate of 120 g (weight after drying) per liter of monolith volume.

(A-6) Performance Evaluation of Catalysts of Examples (1) and (2): Shift Catalysts of Examples (1) and (2) and Shift Catalysts of Comparative Examples (1) to (7) FIG. 7 shows the result of comparing the performances of promoting shift reaction by using. FIG. 7 shows the result of measuring the maximum CO reduction rate described later in order to compare the performance of the shift catalyst.

In order to compare the performances of the catalysts of the above-mentioned examples and the catalysts of the comparative examples, each catalyst constituted by using a monolith was housed in a predetermined reactor, and
A hydrogen-rich gas containing carbon monoxide was supplied as a test gas to cause a shift reaction. The conditions of the gas used for the shift reaction are shown below. Composition of test gas (dry state) ... N2 = 34.7%, H
2 = 46.8%, CO = 6.27%, CO2 = 11.9
%; Water vapor amount (molar ratio) ... H2O / CO = 6.3; Space velocity SV (dry state) = 2,700 / h;

Here, the temperature of the incoming gas (the temperature of the test gas supplied to the reactor containing each catalyst) was changed from 150 ° C to 4 ° C.
The carbon monoxide concentration (CO concentration) in the exhaust gas discharged from the reactor was measured while gradually increasing the temperature to 00 ° C. Then, the CO reduction rate was calculated from the carbon monoxide concentration in the exhaust gas discharged from the reactor. Here, the CO reduction rate means the amount of CO converted into CO ₂ by the shift reaction (the amount of CO in the test gas-the amount of CO in the exhaust gas) and the amount of CO before the reaction (the amount of CO in the test gas). Is expressed as a molar ratio of. The larger the CO reduction rate, the better the catalyst performance for reducing the CO concentration. The maximum CO reduction rate refers to the highest CO reduction rate obtained when the CO concentration in the exhaust gas is measured by sequentially changing the inlet gas temperature as described above and calculating the CO reduction rate.

As shown in FIG. 7, the catalysts of Examples (1) and (2) in which CeO ₂ or WO ₃ was added to TiO ₂ which is the main component of the catalyst carrier were the catalysts of other comparative examples. As a result, the above-mentioned maximum CO reduction rate was high, and the result was excellent in the ability to reduce the CO concentration in the supplied hydrogen-rich gas.

FIG. 8 shows the catalysts of Examples (1) and (2),
Regarding the catalysts of Comparative Examples (1), (6) and (7), the required CO reduction rate changes when the CO concentration in the exhaust gas is measured while sequentially changing the inlet gas temperature as described above. FIG. As shown in FIG. 8, experiments were conducted for the catalysts of Examples (1) and (2), including when the incoming gas temperature was lower than that of the catalysts of Comparative Examples (1) and (6). A high CO reduction rate was exhibited over the entire temperature range.
In addition, the catalysts of Examples (1) and (2) showed a higher CO reduction rate in the temperature range of 250 ° C. or higher than the catalyst of Comparative Example (7).

Similarly, FIG. 9 shows that the catalysts of Examples (1) and (2) and the catalysts of Comparative Examples (2) to (5) were exhausted while the inlet gas temperature was sequentially changed as described above. It is a figure which shows a mode that the required CO reduction rate changes, when measuring the CO concentration in inside. The catalysts of Examples (1) and (2) showed a higher CO reduction rate over the entire temperature range in which the experiment was conducted, even when compared with the catalysts of Comparative Examples (2) to (5).

(A-7) Examination of the amount of added oxide: FIG.
Is CeO added to TiO ₂ which is the main component of the catalyst carrier.
FIG. 4 is a diagram showing the results of examining how the activity of the shift catalyst changes by changing the amount of ₂ ; here,
When a shift catalyst is manufactured by the same method as the catalyst of Example (1) described above, a shift catalyst having different CeO ₂ powder amount added to the TiO ₂ powder is manufactured in the step S100 shown in FIG. Then, the maximum CO reduction rate was examined for each. The shift catalyst used to measure the maximum CO reduction rate is
Ce for the entire mixed powder obtained in step S100
The mixing ratio of O ₂ is 1% by weight, 4% by weight, 10% by weight,
There are five types of catalysts, 20 wt% and 50 wt%.

As shown in FIG. 10, P, which is a catalyst active material,
By further adding CeO ₂ to TiO ₂ supporting t, the maximum CO reduction rate of the shift catalyst was improved over the range of 1 wt% to 50 wt% of CeO ₂ . Especially, the mixing ratio of CeO ₂ is from 1% by weight to 1%.
In the range of 5% by weight, the highest CO reduction rate was extremely high.

Similarly, FIG. 11 is a graph showing the results of investigation of how the maximum CO reduction rate of the catalyst changes by changing the amount of WO ₃ added to TiO ₂ which is the main component of the catalyst carrier. is there. The shift catalyst used for the measurement of the maximum CO reduction rate has a mixing ratio of WO ₃ with respect to the entire mixed powder obtained in step S100 of 1% by weight, 4% by weight,
Five types of catalysts, 6 wt%, 12 wt% and 50 wt%.

As shown in FIG. 11, P, which is a catalyst active material,
TiO carrying t₂And WO ₃When containing
Similarly, WO₃Mixing ratio of 1 to 50% by weight
Improvement of maximum CO reduction rate of shift catalyst over the range of
Was seen. In particular, WO₃Mixing ratio of 1% by weight to 1
In the range of 5% by weight, the highest CO reduction rate is extremely high.
It was

(B) Examples (1), (3) to (9) and Comparative Examples (1), (7): Example (1), shown in FIG.
The catalysts (3) to (9) and the catalysts of Comparative Examples (1) and (7) were produced and their catalytic performances were compared. The catalyst of Example (1) shown in FIG. 12 and Comparative Examples (1) and (7)
Is the catalyst of Example (1) shown in FIG.
And the same catalyst as Comparative Examples (1) and (7).

(B-1) Example (3): The catalyst of Example (3) was produced according to the production method (FIG. 3) shown in the above-described third embodiment. Using the catalyst of Example (3),
When manufacturing in accordance with the manufacturing process shown in FIG. 3, as the process from step S300 to step S350, the same process as the manufacturing process from step S100 to step S150 of the above-described embodiment (1) is performed. A catalyst similar to the above was obtained.

Next, the monolith having the platinum-supporting carrier layer obtained in step S350 is immersed in a solution containing a nitrate of lithium (Li) (step S360) to impregnate and support Li on the platinum-supporting carrier layer. It was Step S36
At 0, the amount of Li impregnated and supported on the carrier layer and the step S
The molar ratio with the amount of Pt supported on the carrier at 340 is L
The solution concentration to be used was adjusted so that i: Pt = 1: 3. The monolith was further dried and calcined (step S370) to complete the catalyst of Example (3). In step S370, drying is performed for 24 hours at 120 ° C.
Baking was performed at 0 ° C. for 2 hours. As a result, TiO ₂
A shift catalyst was obtained in which a layer of a carrier containing Cd and CeO ₂ further contained Li as an additive.

(B-2) Examples (4) to (9): The catalysts of Examples (4) to (9) are used for immersing the monolith on which the platinum-supporting carrier layer is formed in the step S360. , The catalyst was prepared in the same manner as the catalyst of Example (3) above, except that a solution containing a nitrate other than Li was used. The catalyst of Example (4) is sodium (Na), the catalyst of Example (5) is potassium (K), the catalyst of Example (6) is rubidium (Rb), and the catalyst of Example (7) is The catalyst of Example (8) of magnesium (Mg) is calcium (Ca)
As the catalyst of Example (9), a nitrate solution of lanthanum (La) was used. The concentration of the salt solution used was adjusted in the same manner as in Example (3) so that the molar ratio to the amount of Pt supported on the carrier in step S340 was Li: Pt = 1: 3. As a result, TiO ₂ and CeO
A carrier layer containing ₂ and
A shift catalyst containing each of a, K, Rb, Mg, Ca, and La was obtained.

(B-3) Performance Evaluation of Catalysts of Examples (3) to (9): Shift Catalysts of Examples (1), (3) to (9) and Comparative Examples (1) and (7) FIG. 13 shows the results of comparison of the performance of promoting the shift reaction using the shift catalyst of No. 1 shown in FIG. In FIG. 13, in order to compare the performance of the shift catalyst,
The result of having measured the maximum CO reduction rate is shown.

Here, similar to the experimental results shown in FIG. 7, the shift reaction was performed using the test gas under the following conditions, and the inlet gas temperature was gradually increased from 150 ° C. to 400 ° C. The CO reduction rate was calculated. Composition of test gas (dry state) ... N2 = 34.7%, H
2 = 46.8%, CO = 6.27%, CO2 = 11.9
%; Water vapor amount (molar ratio) ... H2O / CO = 6.3; Space velocity SV (dry state) = 2,700 / h;

As shown in FIG. 13, Examples (3)-
The catalyst of (9) showed a higher maximum CO reduction rate than the catalyst of Example (1). That is, TiO ₂ and Ce
In the layer of the carrier containing O ₂ , Li, Na, K,
The maximum CO reduction rate was further improved by further adding any one of Rb, Mg, Ca, and La.

(C) Examples (3) 'to (9)' and Comparative Example (1) ': Catalysts of Examples (3) to (9) produced by using honeycomb, and Comparative Example (1). The catalysts of Examples (3) ′ to (9) ′ and Comparative Example (1) ′, which are pellet-shaped shift catalysts, were produced corresponding to each of the catalysts. The catalysts of Examples (3) ′ to (9) ′ and Comparative Example (1) ′ are the catalysts of Examples (3) to (9) and the catalyst of Comparative Example (1) shown in FIG. 12, respectively. ,
The same additive, catalyst active material, and carrier are provided.

(C-1) Example (3) ': Example
The catalyst of (3) 'is shown in the above-mentioned fourth embodiment.
It was manufactured based on the manufacturing method (FIG. 4). Example (3) '
When the catalyst of is manufactured according to the manufacturing process shown in FIG.
In step S400, Ce is added as an oxide powder.
O₂Powder was used. CeO₂Powder is step S100
In mixed powder obtained by ₂Is 4% by weight
Becomes the amount of TiO₂Mix into powder. Step S41
At 0, the above mixed powder was immersed in a platinum nitrate solution to
Of Pt on the mixed powder by the ion exchange method.
It was The supported amount of Pt is 1.2 g per 120 g of the mixed powder.
And Then, in step S420, 120 ° C.
Dry for 24 hours and bake at 350 ° C for 2 hours.
It was.

After that, the platinum-supported mixed powder obtained in step S420 was immersed in a solution containing a nitrate of Li (step S424), and the mixed powder as the catalyst carrier was impregnated and supported with Li. In step S424, the solution concentration used was adjusted so that the molar ratio of the amount of Li impregnated and supported on the carrier and the amount of Pt supported on the carrier in step S410 was Li: Pt = 1: 3. The platinum-supported mixed powder impregnated with Li is further dried and fired (step S
426), and further compressed and crushed to form pellets (step S430) to complete the catalyst of Example (3) ′. In step S426, it was dried at 120 ° C. for 24 hours and baked at 350 ° C. for 2 hours. As a result, a shift catalyst was obtained in which the catalyst carrier containing TiO ₂ and CeO ₂ further contained Li as an additive.

(C-2) Examples (4) 'to (9)': The catalysts of Examples (4) 'to (9)' are used for immersing the platinum-supported mixed powder in the step S424. , L
It was produced in the same manner as the catalyst of Example (3) ′ above, except that a solution containing a nitrate other than i was used. Example (4) '
Is sodium (Na), the catalyst of Example (5) 'is potassium (K), the catalyst of Example (6)' is rubidium (Rb), and the catalyst of Example (7) 'is magnesium (K). Mg), the catalyst of Example (8) ′ is calcium (C
a), the catalyst of Example (9) ′ is lanthanum (La),
Nitrate solutions were used respectively. The concentration of the salt solution used was adjusted in the same manner as in Example (3) ′ so that the molar ratio with the amount of Pt supported on the carrier in step S424 was Li: Pt = 1: 3. This allows TiO ₂ and C
A carrier containing eO ₂ is further added with N as an additive.
A shift catalyst containing each of a, K, Rb, Mg, Ca, and La was obtained.

(C-3) Comparative Example (1) ': A catalyst of Comparative Example (1)' was produced as a comparative example to the catalysts of Examples (3) 'to (9)'. The catalyst of this Comparative Example (1) 'is in the process of step S400, instead of preparing a mixed powder of additive oxide powder and TiO ₂ powder were prepared TiO ₂ powder without the additive oxide. Further, the steps S424 and S426 are not performed, and the catalyst carrier does not contain the above-mentioned additional element. Other steps were carried out in the same manner as the catalyst of Example (3) ′ above.

(C-4) Evaluation on Adsorption of Water: FIG.
FIG. 4 is an explanatory diagram showing the results of examining the amount of water adsorbed for the catalysts of Examples (3) ′ to (9) ′ and the catalyst of Comparative Example (1) ′. When the catalyst component is changed, the property of the catalyst surface is changed by this, and the force of chemically attracting water to the catalyst surface is changed. In FIG. 14, after removing the water adsorbed on the catalyst surface by physical adsorption, the amount of water adsorbed on the catalyst surface by chemical adsorption was measured,
The magnitude of the force of chemically attracting water to the catalyst surface was evaluated. It is considered that if the force of attracting water to the surface of the catalyst is strong, the concentration of the reactant increases when the shift reaction proceeds on the catalyst, so that the activity of promoting the shift reaction becomes stronger.

To measure the amount of water adsorbed, each of the above catalysts was first placed in water. As a result, water molecules are adsorbed on the surface of each catalyst by physical adsorption and chemical adsorption. After that, place each catalyst under a helium gas atmosphere,
Heated at 120 ° C. for 30 minutes. As a result, water molecules adsorbed on the catalyst surface by physical adsorption were removed. After this, in the same helium gas atmosphere, 100 ° C to 50 ° C.
The temperature was gradually raised to 0 ° C. As a result, water molecules adsorbed on the catalyst surface by chemical adsorption were removed.
At that time, the amount of water removed from the catalyst surface was measured using a mass spectrometer. FIG. 14 is from 100 ° C. to 400
It is a relative representation of the amount of water measured off the catalyst surface when the temperature is raised to ° C.

As shown in FIG. 14, the embodiment (3) '-
It was shown that the catalyst of (9) 'had a larger amount of water adsorbed than the catalyst of Comparative Example (1)'. Example (3) '-
The rank of the amount of water adsorbed on each catalyst of (9) ′ was well correlated with the rank of the highest CO reduction rate of each catalyst shown in FIGS. 12 and 13. When a pellet catalyst provided with an added oxide but no added element (a pellet catalyst corresponding to the catalyst (1)) was prepared and the same measurement was carried out, the amount of water adsorbed was found to be the same as in Example (3) ′. ~
Although the amount was smaller than that of the catalyst of (9) ′, the amount thereof was larger than that of the catalyst of Comparative Example (1) ′ (not shown).

(D) Embodiments (2), (10) to (16)
And Comparative Examples (1) and (7): The catalysts of Examples (2) and (10) to (16) shown in FIG. 15 and the catalysts of Comparative Examples (1) and (7) were produced to improve the catalytic performance. Compared.
The catalyst of Example (2) shown in FIG. 15 and the catalysts of Comparative Examples (1) and (7) are the catalyst of Example (2) shown in FIG. 6 and the Comparative Example (1). ) And (7) are the same catalysts.

(D-1) Example (10): Example (1)
The catalyst of 0) was manufactured based on the manufacturing method (FIG. 3) shown in the above-described third embodiment. The catalyst of Example (10) was manufactured based on the manufacturing method (FIG. 3) shown in the above-described third embodiment. When the catalyst of Example (10) is manufactured according to the manufacturing process shown in FIG.
As the process from 300 to step S350, the manufacturing process steps S100 to S of the embodiment (2) described above are performed.
The same process as in 150 was carried out to obtain a catalyst similar to that of Example (2).

Next, the monolith having the platinum-supporting carrier layer obtained in step S350 is immersed in a solution containing a nitrate of lithium (Li) (step S360) to impregnate and support Li on the platinum-supporting carrier layer. It was Step S36
At 0, the amount of Li impregnated and supported on the carrier layer and the step S
The molar ratio with the amount of Pt supported on the carrier at 340 is L
The solution concentration to be used was adjusted so that i: Pt = 1: 3. The monolith was further dried and calcined (step S370) to complete the catalyst of Example (10). In step S370, drying is performed at 120 ° C. for 24 hours, and then 3
Firing was performed at 50 ° C. for 2 hours. By this, TiO
A shift catalyst was obtained in which the carrier layer containing ₂ and CeO ₂ further contained Li as an additive.

(D-2) Examples (11) to (16): The catalysts of Examples (11) to (16) are used for immersing the monolith formed with the platinum-supporting carrier layer in the step S360. , The catalyst was produced in the same manner as the catalyst of Example (10) above, except that a solution containing a nitrate other than Li was used. The catalyst of Example (11) is sodium (Na), the catalyst of Example (12) is potassium (K), Example (1).
The catalyst of 3) is rubidium (Rb), the catalyst of Example (14) is magnesium (Mg), the catalyst of Example (15) is calcium (Ca), and the catalyst of Example (16) is lanthanum (La). ) Of nitrate solution was used. The salt solution used is the same as in Example (10) above, and the salt solution used in step S3
The molar ratio with the amount of Pt supported on the carrier at 40 is Li: P.
The concentration was adjusted so that t = 1: 3. As a result, a shift catalyst was obtained in which the layer of the carrier containing TiO ₂ and CeO ₂ further contained each of Na, K, Rb, Mg, Ca, and La as an additive.

(D-3) Performance evaluation of catalysts of Examples (10) to (16): Shift catalysts of Examples (2), (10) to (16) and Comparative Examples (1) and (7). FIG. 16 shows the results of comparison of the performance of promoting the shift reaction using the shift catalyst of No. 1 shown in FIG. FIG. 16 shows the result of measuring the maximum CO reduction rate in order to compare the performance of the shift catalyst.

Here, similarly to the experimental results shown in FIGS. 7 and 13, the shift reaction was carried out using the test gas under the conditions shown below, and the inlet gas temperature was changed from 150 ° C. to 400 ° C.
The maximum CO reduction rate was obtained by sequentially increasing the temperature to 0 ° C. Composition of test gas (dry state) ... N2 = 34.7%, H
2 = 46.8%, CO = 6.27%, CO2 = 11.9
%; Water vapor amount (molar ratio) ... H2O / CO = 6.3; Space velocity SV (dry state) = 2,700 / h;

As shown in FIG. 16, Examples (10)-
The catalyst of (16) showed a higher maximum CO reduction rate than the catalyst of Example (2). That is, TiO ₂ and W
In the layer of the carrier containing O ₃ , Li, Na, K,
The maximum CO reduction rate was further improved by further adding any one of Rb, Mg, Ca, and La.

FIG. 17 shows examples (2), (10) to (1).
Regarding the catalyst of 6) and the catalysts of Comparative Examples (1) and (7),
It is a figure which shows a mode that the required CO reduction rate changes, when measuring the CO density | concentration in exhaust gas, changing the entering gas temperature one by one as mentioned above. As shown in FIG. 17, the catalysts of Examples (10) to (14) and (16) were compared to the catalysts of Comparative Examples (1) and (7), including when the incoming gas temperature was lower, Over the temperature range in which the experiment was conducted,
It showed a high CO reduction rate. Further, the catalyst of Example (15) showed a higher CO reduction rate in the temperature range of 230 ° C. or higher than the catalyst of Comparative Example (7). Regarding the catalysts of Examples (3) to (9) described above, the CO concentration in the exhaust gas was measured while the inlet gas temperature was sequentially changed as described above, and the CO reduction rate was also calculated. Results similar to those of the catalysts of Examples (10) to (16) shown in FIG. 17 were shown (not shown).

[Brief description of drawings]

FIG. 1 is a process chart showing a method of manufacturing a shift catalyst according to a first embodiment of the present invention.

FIG. 2 is a process chart showing a method of manufacturing a shift catalyst according to a second embodiment.

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

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

FIG. 5 is an explanatory diagram illustrating a configuration of a fuel cell system having a shift unit including a shift catalyst.

FIG. 6 is an explanatory diagram showing conditions regarding the catalyst of each example and the catalyst of a comparative example.

FIG. 7 shows the catalyst of each Example and the catalyst of Comparative Example,
It is explanatory drawing which shows the result of having compared the maximum CO reduction rate.

FIG. 8: C calculated while sequentially changing the temperature of the incoming gas
It is a figure which shows a mode that the O reduction rate changes.

FIG. 9: C calculated while sequentially changing the inlet gas temperature
It is a figure which shows a mode that the O reduction rate changes.

FIG. 10 is a diagram showing the results of examining how the activity of the shift catalyst changes by changing the amount of CeO ₂ added to TiO ₂ .

FIG. 11 is a diagram showing the results of examining how the activity of the shift catalyst changes by changing the amount of WO ₃ added to TiO ₂ .

FIG. 12 is an explanatory diagram showing conditions relating to the catalyst of each example and the catalyst of the comparative example.

FIG. 13 is an explanatory diagram showing the results of comparing the maximum CO reduction rates of the catalyst of each example and the catalyst of the comparative example.

FIG. 14 is an explanatory diagram showing the results of examining the amount of water adsorbed for the catalyst of each example and the catalyst of the comparative example.

FIG. 15 is an explanatory diagram showing conditions relating to the catalyst of each example and the catalyst of the comparative example.

FIG. 16 is an explanatory diagram showing the results of comparing the maximum CO reduction rates of the catalyst of each example and the catalyst of the comparative example.

FIG. 17 is a diagram showing how the CO reduction rate calculated while sequentially changing the incoming gas temperature.

[Explanation of symbols]

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

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 8/06 B01J 23/56 301M // H01M 8/10 23/64 103M F term (reference) 4G040 EA01 EA02 EA03 EA06 EB32 4G069 AA03 AA08 BA04A BA04B BA13B BC01A BC08A BC43A BC43B BC60A BC60B BC75A BC75B CC26 DA06 EA19 FB26 5H026 AA06 BB04 BB08 EE02 EE12 HH05 5H027 AA06 BA31 BA17 DD00

Claims (12)

[Claims] 1. 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 oxide of cerium (Ce) and tungsten (W). Of the oxide of the above, a step of preparing a carrier made of titania (TiO ₂ ) containing at least one of the oxides, and (b) a step of supporting platinum (Pt) on the carrier. Method. 2. The method for producing a shift catalyst according to claim 1, wherein the step (a) includes: (a-1) a step of producing a mixture of the titania and the oxide, and (a-2) ) A process for producing a shift catalyst, comprising the step of forming the support using the mixture. 3. The method for producing a shift catalyst according to claim 2, wherein in the step (a-2), a predetermined binder is added to the mixture to form a slurry, and the slurry is supported on a predetermined base material. A method for producing a shift catalyst, including the step of: 4. The method for producing a shift catalyst according to claim 2, wherein in the step (a-1), the ratio of the oxide in the mixture is 1 to 50% by weight. A method for producing a shift catalyst for producing the mixture. 5. The method for producing a shift catalyst according to claim 4, wherein in the step (a-1), the ratio of the oxide in the mixture is 1 to 15% by weight. A method for producing a shift catalyst for producing the same. 6. The method for producing a shift catalyst according to claim 1, wherein (c) at least one element selected from the group consisting of an alkali metal element, an alkaline earth metal element and a rare earth element is provided on the carrier. A method for producing a shift catalyst, further comprising the step of adding 7. The method for producing a shift catalyst according to claim 6, wherein the alkali metal element is selected from the group consisting of lithium (Li), sodium (Na), potassium (K), and rubidium (Rb). A method for producing a shift catalyst containing at least one element. 8. The method of manufacturing a shift catalyst according to claim 6, wherein the alkaline earth metal element contains at least one element of magnesium (Mg) and calcium (Ca). Method. 9. The method for producing a shift catalyst according to claim 6, wherein the rare earth element contains lanthanum (La). 10. A shift catalyst having an activity of promoting a shift reaction for producing hydrogen and carbon dioxide from water and carbon monoxide, which is one of oxides of cerium (Ce) and tungsten (W). Of at least one of the titania (T
A shift catalyst comprising a carrier composed of iO ₂ ) and platinum supported on the carrier. 11. The shift catalyst according to claim 10, wherein the ratio of titanium to cerium and / or tungsten in the carrier is cerium oxide (CeO ₂ ) and tungsten oxide (WO ₃ ), respectively. The shift catalyst has a weight ratio of 1 to 50% by weight when converted to. 12. The shift catalyst according to claim 10, further comprising at least one element selected from an alkali metal element, an alkaline earth metal element, and a rare earth element.