JP2003048702A - Carbon monoxide removing apparatus for reducing amount of carbon monoxide in reformed gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon monoxide removing apparatus having a catalyst useful for selectively oxidizing carbon monoxide in a hydrogen-enriched reformed gas with oxygen with which carbon monoxide in the gas can be more efficiently oxidized and the amount of carbon monoxide can be reduced. SOLUTION: The reformed gas supplied into the carbon monoxide removing apparatus 11 is first passed through a catalyst layer 12 constituted of a catalyst A in which ruthenium and platinum are supported on a porous carrier in a weight ratio of ruthenium to platinum of >=0.7 and <=9.5 and ruthenium and platinum are localized in the outer surface of the porous carrier, then the reformed gas is passed through a catalyst layer 13 constituted of a catalyst B in which ruthenium and platinum are supported in a porous carrier in a weight ratio of ruthenium to platinum of >=0.1 and <0.7 and ruthenium and platinum are localized in the outer surface of the porous carrier, and further the reformed gas is passed through a catalyst layer 14 constituted of the above catalyst A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon monoxide removing apparatus for reducing carbon monoxide by utilizing a catalyst for selectively oxidizing carbon monoxide from hydrogen-rich reformed gas with oxygen. The present invention relates to a carbon monoxide removing device used in a fuel cell system having a solid polymer fuel cell.

[0002]

Reformed gas rich in hydrogen is used as hydrogen for fuel in a system using a fuel cell. The reformed gas is produced by using an alcohol-based fuel such as methanol or a hydrocarbon-based fuel such as butane gas, propane gas, methane gas or liquefied petroleum gas as a raw fuel, and subjecting the raw fuel to a water component and a steam reforming reaction. The reformed gas generated by the steam reforming reaction is carbon monoxide (CO
It is a state containing about several percent. On the other hand, since platinum used as an electrode of a fuel cell is easily poisoned by carbon monoxide, it is necessary to reduce the concentration of the reformed gas to a predetermined low concentration.

Among various fuel cells used in the above fuel cell system, the polymer electrolyte fuel cell is 50
It has been noted that it can operate at a low temperature of -100 ° C. This solid polymer fuel cell is expected to have a small size and a short start-up time due to its high output density, and its use in automobiles, small generators, household cogeneration, etc. has been proposed. Since the polymer electrolyte fuel cell has a low operating temperature, carbon monoxide contained in the reformed gas is tens of p
It is necessary to reduce it to pm or less. The reformed gas contains carbon monoxide in an amount of about 1% by volume even if the reforming gas is subjected to a steam reforming reaction and then subjected to a shift reaction. Therefore,
In a system using a fuel cell, a carbon monoxide removing device for reducing carbon monoxide in the reformed gas is provided in a post-process of producing the reformed gas. It is known that the above-mentioned carbon monoxide removing device reduces the carbon monoxide by selectively oxidizing carbon monoxide with oxygen by using alumina catalysts using various platinum group metals.

[0004]

However, the alumina catalyst using a platinum group metal has low selectivity and activity of the oxidation reaction by oxygen, and hydrogen, which is the main component of the reformed gas, is wasted at the same time. This leads to a decrease in fuel utilization efficiency.
Therefore, carbon monoxide is more efficiently oxidized from the hydrogen-rich reformed gas to reduce carbon monoxide, thereby
There is a demand for a carbon monoxide removing device that can achieve high fuel utilization efficiency and power generation efficiency.

The present invention has been made in view of the above circumstances. An object of the present invention is to remove carbon monoxide from a hydrogen-rich reformed gas more efficiently and reduce it. To provide.

[0006]

As a result of intensive studies to achieve the above object, the present inventors found that a catalyst in which ruthenium and platinum were supported on a porous carrier at a predetermined weight ratio was It is suggested that reducing carbon oxide is good. As a result of further studies, the present inventor has found that in the above catalyst, the weight ratio of ruthenium to platinum (Ru /
Pt) supported catalyst A at a ratio of 0.7 or more and 9.5 or less and the weight ratio of ruthenium to platinum (Ru / Pt)
More efficiently by using the catalyst B supported at a ratio of 0.1 or more and less than 0.7 and arranging the catalyst A first in the carbon monoxide remover, then the catalyst B, and then the catalyst A. It has been found that carbon monoxide can be reduced, and the present invention has been completed based on this finding.

The carbon monoxide removing apparatus according to claim 1 is a carbon monoxide removing apparatus equipped with a catalyst for selectively oxidizing carbon monoxide in a hydrogen-rich reformed gas with oxygen. The catalyst layer, through which the reformed gas supplied to the vessel first passes, has a weight ratio of ruthenium to platinum (R
u / Pt) is supported on the porous carrier at a ratio of 0.7 or more and 9.5 or less, and ruthenium and platinum are composed of the catalyst A localized on the outer surface of the porous carrier. The catalyst layer through which the porous gas passes is supported on the porous carrier at a weight ratio (Ru / Pt) of ruthenium to platinum of 0.1 or more and less than 0.7, and ruthenium and platinum are contained in the porous carrier. It is characterized in that the catalyst layer composed of the catalyst B localized on the outer surface and then passing the reformed gas is composed of the catalyst A.

According to the above, the activity of the catalyst A is higher than that of the catalyst B. Therefore, the carbon monoxide removing apparatus arranges the catalyst A in the first catalyst layer on the inlet side of the carbon monoxide remover to activate the activity. Since the temperature rises due to heat generation at this time, the temperature of the reformed gas passes immediately after that, and the catalyst B having a high efficiency at a high temperature is placed immediately after that, so that the efficiency of the selective oxidation reaction is increased. After that, since the reaction for removing carbon monoxide gradually decreases, the carbon monoxide removing apparatus arranges the catalyst A having high activity even at a low temperature on the further downstream side to perform the selective oxidation reaction. It is possible to efficiently reduce carbon monoxide.

A carbon monoxide removing apparatus according to a second aspect is the carbon monoxide removing apparatus according to the first aspect, wherein the temperature of the reformed gas supplied to the carbon monoxide removing device is 100 to 15.
It is characterized by comprising a temperature control means for controlling the temperature to 0 ° C. By the above, in order to supply the reformed gas at a temperature suitable for the first catalyst layer provided on the inlet side of the carbon monoxide remover,
The selective oxidation reaction can be carried out more efficiently.

A carbon monoxide removing device according to claim 3 is the carbon monoxide removing device according to claim 1 or 2, wherein the outer surface of the porous carrier in which the ruthenium and platinum are localized is: It is characterized in that it is within 100 μm. By the above, the activity of the selective oxidation reaction is further enhanced,
It is possible to efficiently reduce carbon monoxide.

A carbon monoxide removing apparatus according to a fourth aspect is the carbon monoxide removing apparatus according to any one of the first to third aspects, wherein the porous carrier contains α-alumina. As described above, since α-alumina can easily localize ruthenium and platinum on the outer surface, the activity of the selective oxidation reaction can be further enhanced, and carbon monoxide can be efficiently reduced.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of the present invention.

The carbon monoxide removing device reduces carbon monoxide (CO) in the reformed gas. The carbon monoxide removing device is used in a fuel cell system having a solid polymer fuel cell 23 that operates at a low temperature of 50 to 100 ° C. Since the polymer electrolyte fuel cell 23 has a low operating temperature, the carbon monoxide contained in the reformed gas is tens of pp.
It is necessary to reduce it to m or less.

The reformed gas is rich in hydrogen produced by the steam reforming reaction of the raw fuel and the water component, and the raw fuel and the water component are introduced into the reformer 21 to cause the steam reforming reaction. Further, the shift reaction by the shifter 22 causes CO
The concentration is reduced to about 1% by volume. The raw fuel is, for example, butane gas, propane gas, methane gas, hydrocarbon gas such as liquefied petroleum gas, kerosene, light oil,
Examples include hydrocarbon-based liquids such as gasoline, and alcohol-based fuels such as methanol and ethanol.

The reformer 21 is filled with a nickel-based, ruthenium-based, rhodium-based reforming catalyst or the like, and is heated by a heater such as a banner provided to perform a steam reforming reaction.
The temperature at which the steam reforming reaction is performed is defined by the type of the raw fuel. For example, when butane gas is used as the raw fuel, it is heated to 600 ° C. or higher in order to perform a good steam reforming reaction. The shifter 22 is filled with a shift catalyst such as a copper-zinc system and the shift reaction is performed at about 200 to 300 ° C.

The above carbon monoxide removing device includes a carbon monoxide remover 11, a reformed gas supply passage 15 for supplying reformed gas to the carbon monoxide remover 11, and air for supplying air to the reformed gas. A supply path 19, a gas temperature controller 17 for adjusting the temperature of the gas flowing in the reformed gas supply path 15, and a gas discharge path 16 for flowing the gas passing through the carbon monoxide remover 11.
Equipped with. The air supply passage 19 is the reformed gas supply passage 15
Connected to. The reformed gas is supplied to the carbon monoxide remover 11 in a state of being mixed with air.

The carbon monoxide remover 11 has three catalyst layers 12, 13, and 14 formed therein. The first catalyst layer 12 through which the reformed gas first passes is formed by supporting the ruthenium on the porous carrier at a weight ratio (Ru / Pt) of ruthenium to platinum of 0.7 or more and 9.5 or less. And platinum with the catalyst A localized on the outer surface of the porous carrier. The second disposed after the first catalyst layer 12
The catalyst layer 13 has a weight ratio of ruthenium to platinum (R
u / Pt) is supported on the porous carrier at a ratio of 0.1 or more and less than 0.7, and ruthenium and platinum are composed of the catalyst B localized on the outer surface of the porous carrier. .
Then, the third catalyst layer 14 arranged thereafter is the first catalyst layer 14.
Similar to the catalyst layer 12 of FIG.

The catalyst A is a catalyst suitable for low temperatures of about 100 to 150 ° C. When the weight ratio (Ru / Pt) of ruthenium to platinum is less than 0.7, the catalyst A may not be suitable for low temperature, and when the weight ratio (Ru / Pt) exceeds 9.5, the activity is remarkably reduced. There is a risk of The catalyst B is a catalyst suitable for a high temperature of about 130 to 220 ° C. In the catalyst B, when the weight ratio of ruthenium to platinum (Ru / Pt) is less than 0.1, the selective activity of carbon monoxide is easily lost as in the case of Pt alone.
If Pt) is 0.7 or more, it may not be suitable for high temperatures. The outer surface of the porous carrier in which the ruthenium and platinum are localized is preferably 100 μm or less, and 20 μm or less.
Within m is more preferable. When the catalyst A and the catalyst B have ruthenium and platinum localized in the above range, the activity of the selective oxidation reaction can be further enhanced and the carbon monoxide can be efficiently reduced.

As the porous carrier for the catalysts A and B, for example, α-alumina, γ-alumina, titania, silica, zirconia, etc. can be used. Among them, the porous carrier preferably contains α-alumina.
The porous carrier containing α-alumina can easily realize the localization of the above ruthenium and platinum in the above range.

The catalyst A and the catalyst B preferably have a ruthenium and platinum particle size of 200 Å or less.
~ 200Å is desirable. When the particle size is 200 Å or less, the activity of the selective oxidation reaction of carbon monoxide is further improved.

Further, it is preferable that the catalyst A and the catalyst B contain a mixture of ruthenium and platinum in a proportion of 0.01 to 10 mass% because the activity of the selective oxidation reaction of carbon monoxide is further improved.

By the way, it can be confirmed by the following method that the catalyst A and the catalyst B realize excellent carbon monoxide reduction at respective temperatures.

As catalyst A, about 0.2% by mass of α / alumina having an average particle diameter of about 2 mm was supported at a ratio of Ru / Pt = 4, and ruthenium and platinum were 50 μm from the outer surface of the α-alumina. The catalyst that was present up to now was made.
A gas obtained by adding 1.5 vol% of oxygen to a reformed gas using butane gas containing 1 vol% of carbon monoxide as a raw fuel was passed through this catalyst at SV = 30000 h ^−1. At 155 ° C., the CO concentration was 300 ppm, but at 110 ° C., the CO concentration was reduced to 50 ppm.

As catalyst B, α / alumina having an average particle size of about 2 mm, Ru / Pt = 0.5
A catalyst in which ruthenium and platinum were present up to 50 μm from the outer surface of α-alumina was prepared by supporting about 0.2% by mass of the above. 1.5% by volume of oxygen was added to the reformed gas using butane gas containing 1% by volume of carbon monoxide as a raw fuel.
When the charged gas was passed through at SV = 30000 h ⁻¹ , the CO concentration was 300 when the gas temperature was 100 ° C.
Although it was 0 ppm, at 170 ° C., the CO concentration was 41.
It was reduced to 2 ppm.

The above-mentioned carbon monoxide device is used to adjust the temperature of the gas to a temperature suitable for the catalyst layer 12 so that the carbon monoxide reactor 1
The catalyst temperature controller 1 is provided on the outer peripheral surface on which the catalyst layer 12 of No. 1 is arranged.
8 is preferably provided. The carbon monoxide remover 11 includes a temperature sensor 41 and measures the temperature of the catalyst layer 12. The carbon monoxide removing device includes a temperature sensor 41.
And the controller 40 are connected to each other via the electric line 43, and the measured temperature is transmitted to the controller 40. Further, in the carbon monoxide removing device, the controller 40 and the catalyst temperature adjuster 18 are connected via an electric line 45. The carbon monoxide device determines whether the temperature of the catalyst layer 12 measured by the controller 40 is within a predetermined temperature range, and the controller 40 sends the electric line 43.
An instruction signal is transmitted to the catalyst temperature adjuster 18 via the to adjust the temperature. Further, the carbon monoxide device is a carbon monoxide device 1
It is more preferable to provide the catalyst temperature adjuster 18a on the outer peripheral surface on which the second catalyst layer 13 is arranged and the catalyst temperature adjuster 18b on the outer peripheral surface on which the third catalyst layer 14 is arranged. Examples of the catalyst temperature adjusters 18, 8a, 18b include a combination of a heater, a heater, an outside air intake means for cooling, and the like.

The carbon monoxide device is equipped with a gas temperature regulator 17 on the outer peripheral surface of the reformed gas supply passage 15 near the inlet of the carbon monoxide remover 11. The carbon monoxide device includes a temperature sensor 42 in the reformed gas supply path 15 near the inlet of the carbon monoxide remover 11 to measure the temperature of the supplied reformed gas. The carbon monoxide removing device is provided with the temperature sensor 4
2 and the controller 40 are connected via an electric line 44,
The measured temperature is transmitted to the controller 40. Further, in the carbon monoxide removing device, the controller 40 and the gas temperature adjuster 17 are connected via an electric line 46. The carbon monoxide device controls the controller 40 so that the temperature of the supplied reformed gas is 100 to 150 ° C. based on the measured temperature result.
Sends an instruction signal to the gas temperature adjuster 17. Examples of the gas temperature regulator 17 include a heater, a heater,
An example is a combination of outside air intake for cooling. Since the carbon monoxide removing device supplies the reformed gas at a temperature suitable for the catalyst A, the selective oxidation reaction can be performed more efficiently.

In the carbon monoxide removing device, when the reformed gas whose temperature is adjusted in the range of 100 to 150 ° C. by the gas temperature adjuster 17 is supplied to the carbon monoxide remover, the first activation is high. The catalyst layer 12 rapidly reacts with air, and the temperature of the gas rises due to the heat of reaction. Immediately after this, the gas passes through the second catalyst layer 13 suitable for high temperature, so that the selective oxidation reaction proceeds efficiently. Then, the gas is introduced into the third catalyst layer 14 when the generation of reaction heat decreases as it proceeds downstream, and the selective oxidation reaction is further sufficiently performed by the catalyst A having high activity even at low temperature. In the carbon monoxide removing device, the catalyst A is arranged in the first catalyst layer 12, the catalyst B is arranged in the second catalyst layer 13, and the catalyst A is arranged in the third catalyst layer 14,
The carbon monoxide can be reduced very efficiently.

The reformed gas in which carbon monoxide is reduced to several tens of ppm or less by the above-mentioned carbon monoxide removing device is supplied to the gas discharge passage 16
And is introduced into the fuel cell 23. The fuel cell 23 has one fuel electrode 25 through the solid polymer membrane 23.
Power can be generated by introducing the reformed gas into the second electrode and oxygen into the other oxygen electrode 24.

The fuel cell system employing the carbon monoxide removing device can realize high fuel utilization efficiency and power generation efficiency.

[0030]

The carbon monoxide removing apparatus of the present invention can reduce carbon monoxide very efficiently. A fuel cell system employing the carbon monoxide removing device can realize high fuel utilization efficiency and power generation efficiency.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

[Explanation of symbols] 11 Carbon monoxide remover 12, 13, 14 Catalyst layer 15 Reformed gas supply path 16 gas discharge channel 17 Gas temperature controller 18 Catalyst temperature controller 19 Air supply path 21 reformer 22 shifter 23 Fuel cell

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C10K 3/00 C10K 3/00 H01M 8/04 H01M 8/04 N 8/06 8/06 G F term ( Reference) 4G040 EA02 EA03 EA06 EB31 EB32 EB42 4G069 AA03 AA08 BA01A BC70A BC75A CC40 DA06 EA02Y EC22X EC29 FA01 FA02 FC08 4H060 AA02 BB11 BB33 CC18 DD01 EE03 FF02 GG02 5H027 AA06 BA17 KK

Claims (4)

[Claims] 1. A carbon monoxide removing apparatus comprising a catalyst for selectively oxidizing carbon monoxide in a hydrogen-rich reformed gas with oxygen, wherein the reformed gas supplied to the carbon monoxide remover is first The catalyst layer that passes through is supported on a porous carrier at a weight ratio of ruthenium to platinum (Ru / Pt) of 0.7 or more and 9.5 or less, and ruthenium and platinum are provided on the outer surface of the porous carrier. The catalyst layer which is composed of the catalyst A localized in the second layer, and through which the reformed gas then passes has a weight ratio of ruthenium to platinum (Ru / Pt) of 0.1 or more,
A catalyst layer composed of a catalyst B supported on a porous carrier at a ratio of less than 0.7 and having ruthenium and platinum localized on the outer surface of the porous carrier, and a reformed gas passing therethrough,
A carbon monoxide removing device comprising the catalyst A. 2. The carbon monoxide removing apparatus according to claim 1, further comprising temperature control means for controlling the temperature of the reformed gas supplied to the carbon monoxide removing device to 100 to 150 ° C. 3. The carbon monoxide removing apparatus according to claim 1 or 2, wherein the outer surface of the porous carrier in which the ruthenium and platinum are localized is within 100 μm. 4. The carbon monoxide removing device according to claim 1, wherein the porous carrier contains α-alumina.