JP2003275589A - Carbon monoxide shift catalyst and hydrogen purification device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell mainly composed of hydrogen for use in a fuel cell.
An object of the present invention is to improve the activity of a carbon monoxide denaturing catalyst for removing CO in a reformed gas containing O and to provide a hydrogen purifier using the same. SOLUTION: A reforming gas supply unit for supplying a reformed gas containing hydrogen and carbon monoxide, and a shift unit having a catalyst 1 for removing CO from the gas supplied from the reformed gas supply unit Wherein the catalyst contains at least one metal selected from the group consisting of W, Mo, and Sn and Pt.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a carbon monoxide shift catalyst and a hydrogen purifier. More specifically, a carbon monoxide denaturing catalyst for removing CO in a reformed gas containing hydrogen monoxide as a main component and containing carbon monoxide (hereinafter, referred to as CO) used for fuel of a fuel cell, and a hydrogen purification apparatus using the same Regarding

[0002]

2. Description of the Related Art Conventionally, hydrogen used in a fuel cell or the like is produced by mixing water vapor with a hydrocarbon fuel such as methane, propane, gasoline, kerosene, an alcohol fuel such as methanol or an ether fuel such as dimethyl ether, It is generated by bringing it into contact with a heated reforming catalyst. Usually, hydrocarbon fuel is reformed at a temperature of about 500 to 800 ° C, and alcohol or ether fuel is reformed at a temperature of about 200 to 400 ° C.

Although CO is generated during reforming, it is modified at high temperature.
The higher the quality, the higher the concentration of CO generated. Especially charcoal
When using hydrogenated fuel, CO concentration is 10% by volume
Before and after. High solid content used for automobiles and households
Operates at a low temperature of 100 ° C or less like a child fuel cell
In the case of fuel cells, the Pt catalyst used in the electrodes
The CO contained in the reformed gas may cause poisoning.
Therefore, the CO concentration before the reformed gas is supplied to the fuel cell
To 100ppm or less, preferably 10ppm or less
You need to do it. Therefore, using a CO shift catalyst, C
CO with O and water ₂Reacts with hydrogen to produce several thousand ppm to several
After reducing the CO concentration to about volume%, CO is methanated
Or by adding a small amount of air to selectively oxidize
CO is removed.

Conventionally, the CO conversion catalyst has been a low temperature CO
As a shift catalyst, a copper-zinc catalyst, a copper-chromium catalyst or the like that can be used at 150 to 300 ° C. is used.
As the shift catalyst, an iron-chromium catalyst that functions at 300 ° C. or higher is used. These CO shift catalysts can be used only as low temperature CO shift catalysts or as high temperature CO shift catalysts depending on the applications such as chemical plants and hydrogen generators for fuel cells.
A combination of a shift catalyst and a low temperature CO shift catalyst was used.

[0005]

However, copper-based C for low temperature is used.
When the O conversion catalyst is used, a very high catalytic activity can be obtained, but it is necessary to perform a reduction treatment to activate it before use. Since heat is generated during the activation treatment, it is necessary to perform pretreatment for a long time while adjusting the supply amount of the reducing gas so that the temperature of the catalyst does not exceed the heat resistant temperature.
Further, once activated, the CO shift catalyst may be oxidized and deteriorated when oxygen is mixed in when the apparatus is stopped. Therefore, it is necessary to take measures such as preventing oxidation. Further, the low temperature CO shift catalyst has low heat resistance and cannot rapidly heat the catalyst when the apparatus is started.
It was necessary to take measures such as gradually increasing the temperature.

On the other hand, when only the high temperature CO shift catalyst is used, the heat resistance is high and there is no problem even if the temperature rises too much, so that heating at the time of starting becomes easy. But C
When the O shift conversion reaction is a temperature-dependent equilibrium reaction and a high-temperature CO shift catalyst that functions only at high temperatures is used, CO
It was difficult to reduce the concentration to 1% or less. for that reason,
There is a problem that the purification efficiency in the CO purification unit connected later is reduced. In addition, in the Fe-Cr-based catalyst, when a rapid oxidation occurs, the activity of the catalyst is reduced, and hexavalent C
Since r is generated, it is necessary to carry out a reduction treatment at a temperature of 350 ° C. or lower before use, and in order to suppress oxidation, keep it in an inert gas atmosphere even at a lower temperature. Is desirable. Also, when reacting, S
If / C is low, iron carbide may be generated in some cases.

[0007] As described above, the conventional technique cannot be sufficiently applied to the use in which the start and stop is frequently repeated because it takes time to start the shift section in the hydrogen generator and the handling is complicated. There was a problem.

In order to solve this, a noble metal catalyst may be used in some cases. Since the noble metal catalyst has higher heat resistance than the copper-based catalyst, it does not significantly deteriorate even when the temperature rises to about 500 ° C. when the apparatus is started. In addition, it is not necessary to carry out a reduction treatment for a long period of time unlike a copper-based catalyst. Further, even if air is mixed in when the apparatus is stopped, the catalyst deterioration is less than that of the copper-based catalyst. However, Pt, Pd, Rh,
Depending on the conditions, the noble metal catalyst containing Ru and Ru as active ingredients also progresses the methanation reaction of CO or carbon dioxide as a side reaction of the CO conversion reaction. As the methanation reaction progresses, hydrogen is consumed, so that the efficiency of the entire apparatus decreases. Usually, in the temperature range of 150 to 450 ° C. where the CO conversion reaction is performed, the methanation reaction becomes more remarkable as the temperature becomes higher, and the methane production rate varies depending on the type of noble metal. This is because the CO adsorption mechanism differs depending on the type of noble metal, and Pd, Rh, and Ru, which have a CO adsorption mechanism in which the methanation reaction easily proceeds, generate methane at a relatively low temperature and undergo a CO conversion reaction. The temperature range that can be performed is narrowed. On the other hand, the Pt-based catalyst used in the present invention hardly causes a methanation reaction and can perform a CO conversion reaction in a wide temperature range. However, the activity of Pt catalyst is
The problem is that the activity is lower than that of the copper-based catalyst, and a catalyst having high activity at a lower temperature is desired.

[0009]

In order to solve the above problems, the carbon monoxide shift catalyst of the present invention is characterized by containing at least one metal selected from the group consisting of W, Mo and Sn, and Pt. And

Further, the present invention is effective when it contains an alloy of Pt and at least one metal selected from the group consisting of W, Mo and Sn.

Further, the present invention is effective when at least one metal selected from the group consisting of W, Mo and Sn and Pt are supported on the oxide containing cerium.

Further, the hydrogen generator of the present invention comprises a reformed gas supply section for supplying a reformed gas containing hydrogen and carbon monoxide, and a C supplied from the reformed gas supply section.
And a shift section having a catalyst for removing O, wherein the catalyst is the carbon monoxide shift catalyst of the present invention.

In the method for producing a carbon monoxide shift catalyst of the present invention, the carrier carrying any of the metals selected from the group consisting of W, Mo, and Sn and Pt is placed under a reducing gas atmosphere or an inert gas atmosphere. It is characterized in that the heat treatment is performed below.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, W, Mo, Sn
Metals such as contribute to activation of water, CO adsorbed on Pt
It is thought to promote the reaction with. W, Mo, S
Although oxides of metals such as n are stable, they can be alloyed with Pt to suppress oxidation of W, Mo, Sn, and the like. The formation of the alloy can be confirmed by performing X-ray diffraction.

It is desirable that these metals are supported on the carrier in a highly dispersed manner. The catalyst carrier is not particularly limited as long as it can support the catalytically active component in a highly dispersed state. Examples of such materials include alumina, silica,
Silica-alumina, magnesia, titania, etc. can be exemplified. In particular, low-temperature activity can be obtained by supporting it on an oxide containing cerium. When cerium oxide is used as a carrier, it has the highest low-temperature activity for the metamorphism reaction and can suppress the methanation reaction. However, cerium oxide has lower heat resistance than carriers such as alumina and zirconia, and is used when the temperature exceeds 600 ° C, or when water condensation occurs when the device is started or stopped. May reduce the catalytic activity. This can be improved by using a complex oxide in which a metal such as Zr or Al is complexed with Ce, the stability of the catalyst carrier can be improved, and the activity decrease can be suppressed. The method of compounding Zr with Ce is not particularly limited, and for example, a coprecipitation method, a sol-gel method, an alkoxide method or the like can be used. Further, when cerium oxide and zirconia form a solid solution and are uniformly compounded, the stability of the carrier is increased and the progress of the methanation reaction is suppressed. This is because when cerium oxide and zirconia exist without forming a solid solution, low heat resistance and methanation reactivity of the respective materials appear. The formation of the solid solution can be confirmed by powder X-ray diffraction measurement, and it can be seen that the smaller the single-phase diffraction line intensity of cerium oxide or zirconia, the more uniformly the solid solution is formed.

As a method for producing these catalysts, Pt is supported on a carrier, and then any metal selected from the group consisting of W, Mo and Sn is supported, and the catalyst is heated under a reducing gas atmosphere or an inert gas atmosphere at a high temperature. It is desirable to perform heat treatment at 500 ° C. or higher. By loading Pt first, higher activity can be obtained as compared with the opposite case.

Next, an embodiment of the hydrogen purifier of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic vertical cross-sectional view showing the structure of a hydrogen purifier according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a catalyst body, which was installed inside the reaction chamber 2. Three
Is a reformed gas inlet from which reformed gas is introduced.
The reformed gas reacted with the CO conversion catalyst body 1 is discharged from the reformed gas outlet. Further, a diffusion plate 5 is installed on the upstream side of the catalyst body 1 so that the reformed gas uniformly flows. Also,
In order to keep the reactor at a constant temperature, the outer periphery was covered with a heat insulating material 6 made of ceramic wool in a necessary portion.

As the catalyst body 1, there was used a cordierite honeycomb coated with a catalyst in which Pt-Sn was supported on CeZr composite oxide.

Next, the operation and characteristics of this embodiment will be described. The fuel used to generate the reformed gas to be supplied to the hydrogen purifier includes natural gas, methanol, gasoline, etc., and the reforming methods include steam reforming in which steam is added and partial reforming in which air is added. However, here, the case where the reformed gas is obtained by steam reforming the natural gas will be described.

The composition of the reformed gas when steam is reformed from natural gas varies somewhat depending on the temperature of the reforming catalyst, but the average value excluding steam is about 80% hydrogen, carbon dioxide, and Each contains about 10% carbon oxide. The reforming reaction of natural gas is carried out at about 500 to 800 ° C, whereas the transformation reaction of CO and steam is carried out at 150 to 3 ° C.
Since the reaction is carried out at about 50 ° C., the reformed gas is supplied after being cooled before the reformed gas inlet 3. The CO concentration after passing through the CO conversion catalyst body 1 is reduced and discharged from the reformed gas outlet 4.

Next, the operating principle of the present embodiment will be described.

The CO conversion reaction is a temperature-dependent equilibrium reaction, and the CO concentration can be reduced as the temperature is lowered. On the other hand, when the temperature becomes low, the reaction rate on the catalyst decreases, and there is a temperature at which the CO concentration has a minimum value.

On the other hand, in the hydrogen purifying apparatus of the present invention, a noble metal catalyst is used as the catalyst body 1, and since it has extremely high heat resistance as compared with the copper-based catalyst, 50 times when starting the apparatus.
There is no significant deterioration even when the temperature rises to about 0 ° C. In addition, it is not necessary to carry out a reduction treatment for a long period of time unlike a copper-based catalyst. Further, even if air is mixed in when the apparatus is stopped, the catalyst deterioration is less than that of the copper-based catalyst.

The catalyst body used was a cordierite honeycomb coated with the catalyst, but the same shape can be obtained by forming the carrier into a pellet shape and impregnating it with a Pt salt to prepare a CO conversion catalyst body. A modified catalyst body having performance is obtained.

[0026]

EXAMPLES The present invention will be described more specifically below based on examples.

Example 1 100% aluminum hydroxide
After firing at 0 ° C. to obtain θ-alumina, Pt is supported by an impregnation method using a dinitrodiamine platinum nitric acid aqueous solution, hydrogen reduction is performed at 800 ° C., and subsequently 1000 ° C. Ar.
Heat treatment was performed in an air stream (catalyst A). Platinum loading is 4wt
%.

On the other hand, Pt was carried on θ-alumina by an impregnation method from a dinitrodiamine platinum nitric acid aqueous solution, and 50
After firing at 0 ° C., subsequently, W was supported by an impregnation method with an ammonium paratungstate aqueous solution,
After hydrogen reduction was carried out at 00 ° C., heat treatment was carried out in an Ar stream at 1000 ° C. (catalyst B). The amount of platinum supported was 4 wt% and the molar ratio of Pt and W was 1: 1.

In the same manner as catalyst B, Mo was supported by ammonium molybdate. The molar ratio of Pt and Mo was 1: 1 (Catalyst C).

Similarly to the catalyst B, Sn was supported by a 15 wt% tin oxide colloidal aqueous solution. Pt and Sn
Was 1: 1 (catalyst D).

When analyzed by XRD, PtW for catalyst B, PtMo for catalyst C, and catalyst D
It was confirmed that PtSn was included in each of the above.

Alumina sol and water were added to this catalyst powder so as to have a solid content of 5 wt%, and the mixture was pulverized to prepare a catalyst slurry. This catalyst slurry has a diameter of 25 m.
A cordierite honeycomb of m and 20 mm in length was coated. It was loaded on the honeycomb so that the loading amount was 3 g / L Pt. The obtained catalyst was installed in a simulated gas test device. This catalyst contains 10% by volume of CO and 10% of carbon dioxide.
A gas in which water vapor was added to a gas containing 80% by volume of hydrogen and 80% by volume of hydrogen so that the dew point was 75 ° C. was introduced. Space velocity (GHS
V) was 1500 h-1. The catalyst layer was heated in an annular furnace, the temperature of the catalyst layer outlet was measured with a thermocouple, the temperature was lowered stepwise from 420 ° C., and the composition of the gas discharged from the catalyst outlet was measured by gas chromatography after removing water vapor. The characteristics were evaluated. For each catalyst (Table 1)
The results are shown in. As shown in the table, platinum, W, Mo,
It was found that the addition of Sn improves the low temperature activity of CO modification reaction. CO above 400 ° C
The concentration depended on the reaction equilibrium.

[0033]

[Table 1]

Example 2 Using Ce _0.2 Zr _0.8 O _X as a carrier, Pt was supported by an impregnation method from a dinitrodiamine platinum nitric acid aqueous solution and heat-treated at 800 ° C. in an Ar stream (catalyst E). The amount of platinum supported was 4 wt%.

On the other hand, Ce _0.2 Zr _0.8 O _X was loaded with Pt from an aqueous solution of dinitrodiamine platinum nitric acid by an impregnation method and baked at 500 ° C., then 15 wt%
Sn was carried by the impregnation method with the tin oxide colloidal aqueous solution, and reduced at 500 ° C., and then heat-treated at 800 ° C. in an Ar stream (catalyst F). The amount of platinum supported was 4 wt%, and the molar ratio of Pt and Sn was 1: 1.

In the same manner as in Example 1, the catalyst was loaded on a honeycomb and the catalytic activity was evaluated. Table 2 shows the activity at 310 ° C. As shown in the table, the activity could be improved by using the oxide containing cerium as the carrier.

[0037]

[Table 2]

Example 3 W was loaded on θ-alumina by an aqueous solution of ammonium paratungstate by an impregnation method and calcined at 500 ° C., and then Pt was loaded by an impregnation method from an aqueous solution of dinitrodiamine platinum nitric acid. Subsequently, hydrogen reduction was performed at 800 ° C., and then heat treatment was performed in a 1000 ° C. Ar flow (catalyst G). The amount of platinum supported is 4
The molar ratio of Pt and W was 1: 1.

Mo was supported by ammonium molybdate in the same manner as the catalyst G (catalyst H). Pt and Mo
The molar ratio was 1: 1.

Similarly to the catalyst G, Sn was supported by a 15 wt% tin oxide colloid aqueous solution (catalyst I).
The molar ratio of Pt and Sn was 1: 1.

In the same manner as in Example 1, the catalyst was loaded on a honeycomb and the catalytic activity was evaluated. The activity at 360 ° C. is shown in Table 3, including the results shown in Table 1. As shown in the table, a highly active catalyst could be obtained by carrying Pt on the carrier, then carrying any metal selected from the group consisting of W, Mo, and Sn and performing heat treatment.

[0042]

[Table 3]

Example 4 A cordierite honeycomb was coated with the catalyst F of Example 2 and placed in the reaction chamber 2 shown in FIG. From the reformed gas inlet 3, carbon monoxide 8
%, Carbon dioxide 8%, steam 20%, and the remaining reformed gas was hydrogen at a flow rate of 10 liters per minute. The honeycomb was loaded so that Pt was 3 g / liter and the space velocity was 800 h-1. The catalyst amount of the reformed gas temperature was controlled, and the composition of the gas discharged from the reformed gas outlet 4 after the reaction with the catalyst body 1 was measured by gas chromatography. The CO concentration and methane concentration at the catalyst temperature of 350 ° C. were 1.5% and 0.80%, respectively. Further, the operation of restarting the apparatus after stopping the apparatus was repeated 10 times, and the CO concentration was measured under the same conditions and found to be 1.5%.

[0044]

As is apparent from the above examples, according to the present invention, a highly active carbon monoxide modification catalyst for removing CO in a reformed gas containing carbon monoxide (hereinafter, CO) and A hydrogen purification device using the same can be provided.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a hydrogen purification device according to a first embodiment of the present invention.

[Explanation of symbols]

1 catalyst 2 reaction chamber 3 Reformed gas inlet 4 Reformed gas outlet 5 diffuser 6 insulation

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C01B 3/48 H01M 8/06 G H01M 8/06 B01J 23/64 103M (72) Inventor Kiyoshi Taguchi Osaka Prefecture 1006 Kadoma, Kadoma, Matsushita Electric Industrial Co., Ltd. (72) Inventor, Kunihiro Ukai Osaka 100, Kadoma, Kadoma, Matsushita Electric Industrial Co., Ltd. F-term (reference) BC51B BC59A BC59B BC60A BC60B BC75A BC75B CC26 DA06 EA19 EC22Y FA01 FA02 FB14 FB19 FB29 FB44 4G140 EA01 EA02 EA03 EA06 EB34 5H027 AA06 BA01 BA17

Claims (5)

[Claims] 1. A carbon monoxide shift catalyst containing Pt and at least one metal selected from the group consisting of W, Mo and Sn. 2. The carbon monoxide shift catalyst according to claim 1, which contains an alloy of Pt and at least one metal selected from the group consisting of W, Mo, and Sn. 3. An oxide containing cerium containing W, Mo, S
at least one metal selected from the group consisting of n and P
The carbon monoxide shift catalyst according to claim 1, wherein t and t are supported. 4. A reformed gas supply unit for supplying a reformed gas containing hydrogen and carbon monoxide, and a shift conversion unit having a catalyst for removing CO from the gas supplied from the reformed gas supply unit. The hydrogen purifier, wherein the catalyst is the carbon monoxide shift catalyst according to claim 1. 5. A method for producing a carbon monoxide shift catalyst, which comprises subjecting a support carrying any one of metals of the group W, Mo and Sn and Pt to heat treatment in a reducing gas atmosphere or an inert gas atmosphere. .