JP2008222501A - Co selective oxidation method and co selective oxidation reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a CO selective oxidation method and a CO selective oxidation reactor to be used for allowing carbon monoxide (CO) included in a reformed gas produced by reforming a hydrocarbon fuel such as city gas, LPG, kerosene and biogas to selectively react with oxygen to be removed, wherein a noble metal-based catalyst for CO selective oxidation is unnecessary. <P>SOLUTION: A Cu-based CO selective oxidation catalyst 17 is formed by depositing CuO as an active metal on a CeO<SB>2</SB>carrier mixed with Al<SB>2</SB>O<SB>3</SB>. A cooling pipe 21 to which a cooling fin 24 is attached is disposed in a square cylindrical chamber 18 having a gas inlet 19 at the lower end and a gas outlet 20 at the upper end, and functioning as a gas passage 16 inside. The both ends of the cooling pipe 21 are made to penetrate through the side walls of the chamber to protrude outward, and are respectively connected to a supply line 22 and a discharge line 23 of cooling water 12. The square cylindrical chamber 18 is charged with the Cu-based CO selective oxidation catalyst 17, and the gas inlet 19 and the gas outlet 20 are sealed with a porous catalyst receiving plate 25 to form the CO selective oxidation reactor 15. By allowing a reformed gas 8 of hydrocarbon fuel with addition of oxygen or air to flow in the gas passage 16 and bringing into contact with the Cu-based CO selective oxidation catalyst 17, CO in the reformed gas 9 is selectively oxidized to reduce the CO concentration. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention removes carbon monoxide (CO) contained in reformed gas produced by reforming hydrocarbon fuels such as city gas, LPG, kerosene, and biogas by selectively reacting with oxygen. The present invention relates to a CO selective oxidation method and a CO selective oxidation reactor used for the purpose.

  Among fuel cells, reformed gas fuel cells such as solid polymer fuel cells are reformed from hydrocarbon-based fuels such as city gas, LPG, kerosene, and biogas to produce hydrogen-rich reformed gas ( Fuel gas) is supplied to the fuel electrode (anode) of the fuel cell. However, carbon monoxide (CO) contained in the reformed gas produced by reforming the hydrocarbon fuel is a poisonous substance for the electrode catalyst of the fuel cell. It is necessary to remove in advance before supplying the fuel electrode.

Therefore, in a polymer electrolyte fuel cell power generation system and a polymer electrolyte fuel cell cogeneration system, a shift converter (shift reaction) is usually provided downstream of a reformer that performs the reforming process of the hydrocarbon fuel. And a CO 2 removal section comprising a CO removal reactor. As a result, the CO in the reformed gas produced by the reformer is first subjected to a shift reaction of CO + H ₂ O → CO ₂ + H _{2 in the} shift converter, so that the CO concentration in the reformed gas is increased. Is to be reduced. Further, the CO remaining in the reformed gas after passing through the shift converter is further reduced in the CO concentration in the CO removal reactor.

  As a CO removal system in the CO removal reactor, a CO selective oxidation reaction and a methanation reaction are known.

In the CO removal method by the CO selective oxidation reaction, oxygen (O ₂ ) or air is supplied from the outside as a combustion support agent to the reformed gas after the shift reaction discharged from the shift converter, the CO remaining, by selectively reacted with the _{O 2 (O 2} in air) in the presence of a CO selective oxidation catalyst, intended to remove CO by 2CO + _{O 2} → 2CO ₂ becomes oxidation reaction, As the CO selective oxidation catalyst, generally, a noble metal catalyst using platinum (Pt), ruthenium (Ru), or rhodium (Rh) as an active metal is used (for example, Patent Documents 1, 2, and 3). 4).

On the other hand, in the CO removal method by methanation reaction, CO remaining in the reformed gas is reacted with H ₂ in the reformed gas in the presence of a catalyst for methanation reaction, and CO + 3H ₂ → CH ₄ + H ₂ O removes CO by a methanation reaction. As the catalyst for the methanation reaction, platinum (Pt), rhodium (Rh), nickel (Ni), cobalt (Co) is used as an active metal. (For example, refer to Patent Document 5).

By the way, both the selective oxidation reaction of CO and the methanation reaction are exothermic reactions. Of these, the methanation reaction generates heat faster than the selective oxidation reaction, and is a reactant that reacts with CO. Since H ₂ is contained in a large amount in the reformed gas, thermal runaway tends to occur and control is difficult.

On the other hand, the CO selective oxidation reaction generates heat slower than the methanation reaction, and stops the supply of O ₂ or air to stop the supply of O ₂ or air to stop the input of O ₂ , which is a reaction product with CO. Then, since the progress of the CO selective oxidation reaction can be stopped, the controllability is good. For this reason, a CO selective oxidation reactor has been widely used as the CO removal reactor.

  FIG. 7 shows an outline of an example of a fuel processing apparatus of a type provided with a CO selective oxidation reactor as a CO removal reactor, and a reformer for performing reforming (steam reforming) processing of hydrocarbon fuel 1. 2, a CO selective oxidation reactor (CO removal) having a shift converter 4 having a catalyst layer 4 a filled with a shift reaction catalyst, a heat exchanger 5, and a catalyst layer 6 a filled with a CO selective oxidation catalyst. The CO removal device 3 is provided in the vertical container in order from above.

An anode 7a of the polymer electrolyte fuel cell 7 is connected to the downstream side of the CO selective oxidation reactor 6 of the fuel processor. As a result, the reformed gas 8 produced by reforming the hydrocarbon-based fuel 1 with the reformer 2 is guided to the shift converter 4 and is contained in the reformed gas 8 at a reaction temperature of about 250 ° C. CO is shifted to reduce the CO concentration to about 1% or less. Thereafter, the reformed gas 8 after the shift reaction is guided to the CO selective oxidation reactor 6 in a state where a required amount of O ₂ or air 13 is supplied as a combustion support agent, and is reformed at a reaction temperature of about 100 to 150 ° C. The CO concentration in the reformed gas 8 is reduced to 10 ppm or less by selectively oxidizing (combusting) the CO remaining in the gas 8 and converting it into CO ₂ .

  A cooling pipe 9 is disposed in the CO selective oxidation catalyst layer 6 a of the CO selective oxidation reactor 6. Further, on the downstream side of the cooling pipe 9, the cooling pipe 10 is arranged to pass through the heat exchanger 5, and the shift reaction catalyst layer 4 a in the shift converter 4 is arranged to pass therethrough. As a configuration in which the cooling pipe 11 is connected in order, the cooling water 12 is circulated through the cooling pipe 9 of the CO selective oxidation reactor 6, the cooling pipe 10 of the heat exchanger 5, and the cooling pipe 11 of the shift converter 4 in order. You can make it. Thus, in the CO selective oxidation reactor 6, the CO selective oxidation catalyst layer 6 a filled therein is cooled by the cooling water 12 flowing through the cooling pipe 9 to take away the CO selective oxidation reaction heat. Thus, the layer 6a of the CO selective oxidation catalyst is maintained at about 100 to 150 ° C., which is a temperature at which the CO selective oxidation reaction activity is increased.

  In the heat exchanger 5, the cooling water 12 that has been heated after being used for cooling the CO selective oxidation catalyst layer 6 a of the CO selective oxidation reactor 6 is circulated through the cooling pipe 10, so that the shift converter 4 The temperature of the reformed gas 8 after the shift reaction treatment is cooled to a temperature suitable for the CO selective oxidation reaction in the CO selective oxidation reactor 6.

  Further, in the shift converter 4, the cooling water 12 whose temperature has been further increased by being supplied to the cooling of the reformed gas 8 in the heat exchanger 5 is circulated through the cooling pipe 11 to be filled therein. The shift reaction catalyst layer 4a is cooled to remove the shift reaction heat, so that the shift reaction catalyst layer 4a is maintained at about 250 ° C., which is the reaction temperature of the shift reaction.

  Reference numeral 14 denotes water vapor generated when the cooling water 12 rises in temperature as it is used for cooling the CO selective oxidation reactor 6, the heat exchanger 5, and the shift converter 4 (see, for example, Patent Document 6). .

  In the previous application (Japanese Patent Application No. 2006-103999), the present applicant used the steam generated by the water evaporator by utilizing the exhaust heat of the reformer to reform the fuel for steam reforming. In the same manner as described above, the steam generated by supplying the cooling water to the CO selective oxidation reactor and the shift converter is supplied to the reformer together for use in the steam reforming of the fuel. Propose to be.

JP 2001-89101 A JP 2003-340280 A JP 2004-307242 A JP 2005-67917 A JP 2006-239551 A JP 2002-134146 A

  However, as described above, since the CO selective oxidation catalyst used in the conventional CO selective oxidation reaction uses expensive noble metals such as Pt, Ru, and Rh as active metals, the cost required for the CO selective oxidation catalyst increases. Therefore, the cost required for this CO selective oxidation catalyst occupies a relatively large specific weight with respect to the manufacturing cost of the fuel processing apparatus equipped with the CO selective oxidation reactor.

  Therefore, in order to reduce the cost of the fuel processing apparatus, and further to reduce the cost of the solid polymer fuel cell power generation system and the solid polymer fuel cell cogeneration system, the precious metal-based CO selective oxidation catalyst as described above can be used. It is desired to reduce the amount used.

Furthermore, in the case of a catalyst in which a noble metal such as Pt, Ru or Rh is an active metal, when the reaction temperature rises above 150 ° C. which is set as the upper limit of the CO selective oxidation reaction activity (temperature) region, the selective oxidation of CO The selectivity of the reaction decreases, and the methanation reaction activity due to CO and H ₂ increases. As described above, this methanation reaction is an exothermic reaction, and since H ₂ which is a reactant that reacts with CO is present in a large amount in the reformed gas, once the methanation reaction starts, Since there is a concern that the methanation reaction may accelerate and lead to uncontrollable thermal runaway, countermeasures are required.

In the CO selective oxidation reaction, since O ₂ or air is supplied as a combustion support agent, an oxidation reaction of the active metal of the base metal occurs even if an attempt is made to employ a catalyst using an inexpensive base metal as the active metal. As a result, problems such as deterioration of catalyst activity and catalyst performance occur.

  Therefore, as a result of repeated efforts and research to enable the CO selective oxidation reaction to be promoted over a long period of time even when an inexpensive base metal is used as the active metal of the CO selective oxidation catalyst, The inventors have found that the CO selective oxidation reaction can be promoted with high efficiency over a long period of time by a specific combination of a base metal active metal material and a carrier material.

  Therefore, an object of the present invention is to reduce the CO concentration in the reformed gas over a long period of time with high efficiency and to reduce the cost required for the CO selective oxidation catalyst. A CO selective oxidation method and a CO selective oxidation reactor are provided.

  In order to solve the above-described problems, the present invention provides a hydrogen-rich reformed gas obtained by reforming a hydrocarbon-based fuel so that copper oxide is supported as an active metal on a cerium oxide support in the presence of a required amount of oxygen. A CO selective oxidation method in which carbon monoxide in the reformed gas is selectively oxidized and removed by contacting with a Cu-based CO selective oxidation catalyst, and a hydrogen-rich modified reformed hydrocarbon-based fuel. CO selective oxidation reaction having a structure in which a Cu-based CO selective oxidation catalyst formed by supporting copper oxide as an active metal on a cerium oxide support is exposed in a gas flow path for passing a gas. Use a vessel.

  Further, in the above, as a support for the Cu-based CO selective oxidation catalyst, a support obtained by mixing cerium oxide with aluminum oxide at a mixing ratio of 20 mol% or less in terms of a molar percentage converted to cerium and aluminum is used.

  Further, as the Cu-based CO selective oxidation catalyst in each of the above-described configurations, a Cu-based CO selective oxidation catalyst in which copper oxide is supported on a support so that the weight ratio with respect to the whole catalyst is 2.0 to 20.0% is used. To do.

  In each configuration described above, the Cu-based CO selective oxidation catalyst is brought into contact with the reformed gas under a temperature condition of 150 ° C. to 250 ° C.

  Further, in each of the above-described configurations, the anode inlet side of the polymer electrolyte fuel cell is connected to the outlet side of the gas flow path via a heat exchanger for cooling the reformed gas temperature; To do.

According to the present invention, the following excellent effects are exhibited.
(1) A Cu-based CO selective oxidation catalyst in which a hydrogen-rich reformed gas obtained by reforming a hydrocarbon-based fuel is supported on a cerium oxide support as an active metal in the presence of a required amount of oxygen. CO selective oxidation method for selectively oxidizing and removing carbon monoxide in the reformed gas by contacting the gas, and gas flow for circulating a hydrogen-rich reformed gas obtained by reforming a hydrocarbon fuel Since it is a CO selective oxidation reactor characterized by having a structure in which a Cu-based CO selective oxidation catalyst formed by supporting copper oxide as an active metal on a cerium oxide support is exposed in the channel. Since the active metal of the CO selective oxidation catalyst is made of Cu, which is a base metal, a noble metal-based CO selective oxidation catalyst can be dispensed with, and the cost required for the catalyst can be greatly reduced.
(2) Further, by using a Cu-based CO selective oxidation catalyst, the control temperature is compared with a control temperature of 100 ° C. to 150 ° C., which is required when a conventional noble metal-based CO selective oxidation catalyst is used. Can be increased. For this purpose, the cooling capacity required for cooling the Cu-based CO selective oxidation catalyst in the CO selective oxidation reactor is the same as that for cooling the noble metal-based CO selective oxidation catalyst in the conventional CO selective oxidation reactor. It is possible to reduce the cooling capacity required for the above. Furthermore, for the CO selective oxidation reactor using the Cu-based CO selective oxidation catalyst, the reformed gas after the shift reaction treatment by the shift converter provided on the upstream side can be supplied without much lowering the temperature. Therefore, the cooling capacity of the reformed gas required for the shift converter and the heat exchanger provided on the upstream side of the CO selective oxidation reactor can be reduced as compared with the conventional case. Therefore, the cooling area of the Cu-based CO selective oxidation catalyst in the CO selective oxidation reactor can be reduced, and further, the cooling area of the shift reaction catalyst in the shift converter can be reduced. The volume of the cooling structure can be reduced by simplifying the cooling structure in the reactor and the shift converter, so that the volume of the CO selective oxidation reactor and the shift converter itself can be reduced. It becomes feasible to reduce the cost of the apparatus.
(3) As a support for the Cu-based CO selective oxidation catalyst, by using a support obtained by mixing cerium oxide with aluminum oxide at a mixing ratio of 20 mol% or less in terms of a mole percentage converted to cerium and aluminum, The CO selective oxidation activity of the Cu-based CO selective oxidation catalyst can be improved.
(4) By using a Cu-based CO selective oxidation catalyst in which copper oxide is supported on a carrier so as to be 2.0 to 20.0% by weight ratio to the whole catalyst as a Cu-based CO selective oxidation catalyst. Further, it becomes possible to further improve the CO selective oxidation activity of the Cu-based CO selective oxidation catalyst.
(5) By making the Cu-based CO selective oxidation catalyst come into contact with the reformed gas under a temperature condition of 150 ° C. to 250 ° C., the CO selective oxidation reaction of the reformed gas can be performed efficiently. it can.
(6) By adopting a configuration in which the anode inlet side of the polymer electrolyte fuel cell is connected to the outlet side of the gas flow path via a heat exchanger for cooling the temperature of the reformed gas, Even if the CO selective oxidation reactor using the system CO selective oxidation catalyst is controlled at a temperature higher than the control temperature when the conventional noble metal-based CO selective oxidation catalyst is used, the CO selective oxidation reaction The temperature of the reformed gas delivered from the vessel can be easily cooled to a temperature below the temperature limit of the polymer electrolyte fuel cell and then supplied to the anode of the polymer electrolyte fuel cell.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

1 (a) (b) to FIG. 5 show one embodiment of a CO selective oxidation method and a CO selective oxidation reactor of the present invention. Briefly, cerium oxide (CeO ₂ ) is used as a carrier, and CO selective oxidation comprising CO selective oxidation catalyst (hereinafter referred to as Cu-based CO selective oxidation catalyst) 17 having copper oxide (CuO) supported on the support as an active metal in a state exposed to gas flow path 16 The reactor 15 is configured so that the reformed gas 8 produced by reforming a hydrocarbon-based fuel such as city gas, LPG, kerosene, or biogas in the gas flow path 16 is supplied with a required amount of O ₂ or The air 13 is circulated in a mixed state as a combustion support agent, and the CO in the reformed gas 8 is selectively reacted (oxidized) with O _{2 in} the presence of the Cu-based CO selective oxidation catalyst 17 to produce CO _2. The CO concentration in the reformed gas 8 by generating So as to reduce.

More specifically, the Cu-based CO selective oxidation catalyst 17 has a content of CuO, which is an active metal, of 2.0% to 20.0%, preferably 8.0% by weight ratio to the whole catalyst. To do. The content of CuO was set in this way as shown in FIG. 3 in terms of the relationship between the catalyst temperature [° C.] and the CO removal rate (CO reaction rate) [%] obtained at this temperature. When the content of CuO in the oxidation catalyst is variously changed to 2.0% (line A), 5.0% (line B), 8.3% (line C), and 20.0% (line D) As is clear from the results of the respective investigations, if the CuO content is in the range of 2.0% to 20.0%, it can be used as a CO selective oxidation catalyst in the required activation temperature range of 150 ° C. or higher. Sufficient CO removal rate can be obtained. Further, when the CuO content is about 8.0%, the CO removal rate becomes the highest, while when the CuO content is less than 2.0%, the obtained CO removal This is because the rate decreases and becomes insufficient for use as a CO selective oxidation catalyst. Further, if it exceeds 20.0% is to CuO is not easily physically carried on CeO _2.

  In FIG. 3, the result when the CuO content is set to 8.3% is shown as the line C. However, the inventors subsequently set the CuO content more easily (preparation). The Cu-based CO selective oxidation catalyst 17 which is easy to be 8.0% was examined, and as a result, a high CO removal rate similar to that obtained when the CuO content was 8.3% was obtained. It has also been found that good results can be obtained in the reaction stability performance confirmation test (life test) conducted by the present inventors.

Furthermore, it is desirable that alumina (Al ₂ O ₃ ) is mixed in the CeO ₂ support for supporting the active metal CuO for the purpose of improving the specific surface area of the active metal CuO. . This is because the addition of Al ₂ O ₃ is effective for miniaturization of CuO. In this case, the mixing ratio of Al ₂ O ₃ to CeO ₂ is the mole percentage (mol% = Al [mol] / (Al [mol] + Ce [mol])) × 100 in terms of Al and Ce, respectively. In the present specification, all the descriptions of mol% are the same.), So that the upper limit is 20 mol%, and preferably, a support in which 10 mol% of Al ₂ O ₃ is mixed with CeO ₂ is used. . In this way, the mixing ratio of Al ₂ O ₃ to CeO ₂ in the support was set under the condition that the content of CuO as the active metal was fixed at 8.0% by weight with respect to the whole catalyst. As shown in FIG. 4, the relationship between the catalyst layer temperature [° C.] and the CO reaction rate [%] obtained at the temperature is expressed as follows: the mixing ratio of Al ₂ O ₃ to CeO ₂ in the support of the Cu-based CO selective oxidation catalyst is 0 mol%. (line E), 3 mol% (line F), 10 mol% (line G), as is clear from the results of examining each case where was varied 20 mol% and (line H), the carrier consisting of only CeO ₂ (line In the case of using E), the control temperature range (active temperature range) for obtaining a CO reaction rate of, for example, 95% or more, which is desired for use as a CO selective oxidation catalyst, is relatively narrow, whereas CeO ₂ in A ₂ O ₃ by mixing carrier in a range of up to 20 mol% (line F, a line G, a line H) in the case of using a controlled temperature range (the activation temperature for obtaining the above and CO reaction rate of 95% or more in the same manner In particular, when using a support in which the mixing ratio of Al ₂ O ₃ is 10 mol%, the active temperature range can be widened even in a high temperature range, and the upper limit temperature of the control temperature range can be increased. On the other hand, if the mixing ratio of Al ₂ O ₃ with respect to CeO ₂ exceeds 20 mol% in terms of Al and Ce, the refinement of CuO slows down and becomes insufficient for use as a CO selective oxidation catalyst. It is.

From the above, the optimum composition of the Cu-based CO selective oxidation catalyst 17 used in the present invention is 8% CuO / 10 mol% Al ₂ O ₃ —CeO ₂ . According to the Cu-based CO selective oxidation catalyst 17 having such a composition, a CO selective oxidation reaction similar to that of a conventional noble metal-based CO selective oxidation catalyst can be performed at a control temperature (activation temperature range) of 150 ° C. to 250 ° C. It becomes like this. This is apparent from the results of the reaction stability performance confirmation test in which the change in the CO reaction rate with the progress of the reaction time shown in FIG. 5 is examined. It has been found that it can be obtained stably.

When producing the Cu-based CO selective oxidation catalyst 17 having the composition as described above, impregnation method and widely known in the field of catalysts, using a coprecipitation method, CeO 2 such described _above, or, in the CeO ₂ The Cu-based CO selective oxidation catalyst 17 may be adjusted by supporting CuO, which is an active metal, on a carrier having a component obtained by mixing Al ₂ O ₃ at a required ratio. Further, as the shape, a shape corresponding to the usage form such as a pellet shape, a honeycomb shape, or a plate shape may be appropriately selected.

  Next, a specific configuration of the CO selective oxidation reactor 15 of the present invention will be described. FIGS. 1 (a) and 1 (b) show an apparatus configuration in the case of using a pellet-shaped Cu-based CO selective oxidation catalyst 17, and the lower end opening of the rectangular tube container 18 in the vertical direction is the gas inlet 19 and the upper end opening. A gas flow path 16 extending from the gas inlet 19 to the gas outlet 20 is formed inside the rectangular tube container 18 with the portion serving as a gas outlet 20. Further, a cooling pipe 21 having a required shape, for example, an upper end portion of the rectangular tube container 18 is alternately bent at a position near the left wall and a position near the right wall of the rectangular tube container 18 inside the rectangular tube container 18. A plurality of, for example, three meandering cooling pipes 21 extending from the lower end to the lower end are disposed at a required interval in the front-rear direction. The upper and lower ends of each cooling pipe 21 penetrate the side wall (right side wall in the figure) of the rectangular tube container 18 and project outside, and the upper ends of the respective cooling tubes 21 projecting outside the rectangular tube container 18. Are connected in parallel to the cooling water supply line 22, and the lower end of each cooling pipe 21 is connected in parallel to the cooling water discharge line 23.

  The required dimensions project in the radial direction at the required positions of the portions of the respective cooling pipes 21 located inside the rectangular tube container 18, for example, the vertical and horizontal positions of the outer peripheral surface of the portions of the respective cooling pipes 21 extending in the left-right direction. Each cooling fin 24 to be attached is attached.

  Furthermore, the space inside the rectangular tube container 18 is filled with the Cu-based CO selective oxidation catalyst 17 formed in a pellet form, and the gas inlet 19 at the lower end and the gas outlet 20 at the upper end of the rectangular tube container 18 are filled. The CO selective oxidation reactor 15 is configured by attaching catalyst receiving plates 25 each having a large number of through holes having a diameter smaller than that of the pellet-shaped Cu-based CO selective oxidation catalyst 17.

  When using the CO selective oxidation reactor 15 having the above configuration, for example, a fuel processing apparatus as shown in FIG. 2 is configured.

  Specifically, the reformer 2 is connected to a fuel supply line 26 and a water vapor supply line 29 that guides the water vapor 28 from a water evaporator 27 that generates the water vapor 28 using the exhaust heat of the reformer 2. . At the downstream side of the reformer 2, the shift converter 4 configured to cause a shift reaction at a reaction temperature of about 250 ° C., similar to that shown in FIG. 7, is discharged from the shift converter 4. A heat exchanger 5 for reducing the temperature of the reformed gas 8 to a temperature suitable for the CO selective oxidation reaction in the downstream CO selective oxidation reactor 15 is provided in order, and the reformed gas in the heat exchanger 5 is further provided. The gas inlet 19 of the CO selective oxidation reactor 15 having the configuration shown in FIGS.

  On the downstream side of the cooling water discharge line 23 connected to the cooling pipe 21 of the CO selective oxidation reactor 15, the cooling pipe 10 disposed in the heat exchanger 5 and the shift in the shift converter 4. Cooling pipes 11 arranged so as to pass through a layer of reaction catalyst (not shown) are connected in order. The diameters and lengths of the cooling pipes 21, 10, and 11, and the temperature, flow rate, and pressure of the cooling water 12 supplied from the cooling water supply line 22 to the cooling pipe 21 of the CO selective oxidation reactor 15. Is capable of maintaining the temperature of the Cu-based CO selective oxidation catalyst 17 charged in the CO selective oxidation reactor 15 in an active temperature range of 150 ° C. to 250 ° C., and the shift reaction catalyst (see FIG. (Not shown) is set so that the temperature can be maintained at about 250 ° C.

  One end that is the upstream end of the steam line 30 is connected to the downstream side of the cooling pipe 11 of the shift converter 4, and the other end that is the downstream end of the steam line 30 is connected to the steam supply line. 29 is connected to the position immediately upstream of the reformer 2. Thereby, the cooling water 12 supplied to the cooling pipe 21 of the CO selective oxidation reactor 15 through the cooling water supply line 22 is used for cooling the CO selective oxidation reactor 15 and cooling the shift converter 4. The steam 14 generated by this is guided to the steam supply line 29 through the steam line 30 and supplied to the reformer 2 together with the steam 28 guided from the water evaporator 27 through the steam supply line 29. The reformer 2 can be used for steam reforming of the hydrocarbon fuel 1.

  Further, the active temperature range of the Cu-based CO selective oxidation catalyst 17 used in the CO selective oxidation reactor 15 is 150 ° C. to 250 ° C., and the active temperature range of the conventional noble metal-based CO selective oxidation catalyst is 100 ° C. to 150 ° C. Considering that the temperature is higher than the temperature range, the heat exchanger 31 is provided on the downstream side of the CO selective oxidation reactor 15, and the reformed gas 8 is placed on the downstream side of the heat exchanger 31. The humidifier 32 for humidification and the anode 7a of the polymer electrolyte fuel cell 7 are connected in order. As a result, the CO concentration was reduced by the CO selective oxidation reaction in a state where the CO selective oxidation reactor 15 was controlled at a control temperature of 150 ° C. to 250 ° C., which is the activation temperature range of the Cu-based CO selective oxidation catalyst 17. Thereafter, the reformed gas 8 discharged from the CO selective oxidation reactor 15 is subjected to a temperature limit of the polymer electrolyte fuel cell 7 in the heat exchanger 31, for example, a temperature set to 80 ° C. to 90 ° C. After cooling to a temperature below the limit, the cooled reformed gas 8 is humidified by the humidifier 32 and then supplied to the anode 7 a of the polymer electrolyte fuel cell 7.

  33 is a water supply line provided with a pump 35 for supplying water 34 to the water evaporator 27, and 36 is a pump provided in the cooling water supply line 22. 2 that are the same as those shown in FIG. 7 are denoted by the same reference numerals.

  According to the fuel processing apparatus having the above configuration, when the reformer 2 steam-reforms the hydrocarbon-based fuel 1 to generate the hydrogen-rich reformed gas 8, the reformed gas 8 is By contacting the shift reaction catalyst (not shown) which is guided to the shift converter 4 and maintained at a reaction temperature of about 250 ° C. by the cooling water 12 flowing through the cooling pipe 11 of the shift converter 4, the reforming is performed. The CO contained in the gas 8 undergoes a shift reaction to reduce the CO concentration.

  Thereafter, the reformed gas 8 discharged from the shift converter 4 is guided to the heat exchanger 5 and is selectively oxidized in the downstream CO selective oxidation reactor 15 by the cooling water 12 flowing through the cooling pipe 10. The temperature is adjusted to a temperature suitable for the reaction.

Thereafter, the reformed gas 8 that has passed through the heat exchanger 5 is added with a required amount of O ₂ or air 13 as a combustion support agent, and then into the gas flow path 6 from the gas inlet 19 of the CO selective oxidation reactor 15. When supplied, the gas flow path 16 is brought into contact with the Cu-based CO selective oxidation catalyst 17 whose temperature is controlled so as to be maintained in the active temperature range of 150 ° C. to 250 ° C. by the cooling water 12 flowing through the cooling pipe 21. The CO contained in the reformed gas 8 is selectively reacted with O ₂ to become CO ₂ , thereby further reducing the CO concentration.

  Thereafter, the reformed gas 8 whose CO concentration has been reduced by the CO selective oxidation reaction in the Cu-based CO selective oxidation reactor 15 is reduced below the temperature limit of the polymer electrolyte fuel cell 7 in the heat exchanger 31. After the temperature is lowered, the air is supplied to the anode 7 a of the polymer electrolyte fuel cell 7 while being humidified by the humidifier 32.

  As described above, the CO selective oxidation reactor 15 uses the CO selective oxidation catalyst 17 in which the active metal is based on Cu, which is a base metal. Therefore, compared with the case where a noble metal based CO selective oxidation catalyst is used. Thus, the cost required for the catalyst can be greatly reduced.

  Further, since the control temperature can be set from 150 ° C. to 250 ° C. by using the Cu-based CO selective oxidation catalyst 17, the conventional CO selective oxidation reactor using a noble metal-based CO selective oxidation catalyst can be used from 100 ° C. By increasing the control temperature as compared with the control temperature of 150 ° C., the cooling capacity required for cooling the Cu-based CO selective oxidation catalyst 17 in the CO selective oxidation reactor 15 can be increased by the conventional CO selective oxidation reaction. The cooling capacity required for cooling the noble metal-based CO selective oxidation catalyst used in the vessel can be reduced.

  Further, the reformed gas 8 after the shift reaction process by the shift converter 4 provided on the upstream side of the CO selective oxidation reactor 15 is supplied to the CO selective oxidation reactor 15 without reducing the temperature so much. Therefore, the cooling capacity of the reformed gas 8 required for the shift converter 4 and the heat exchanger 5 can be reduced as compared with the conventional case.

  Therefore, the cooling area of the Cu-based CO selective oxidation catalyst 17 in the CO selective oxidation reactor 15 can be reduced, and further, the cooling area of the shift reaction catalyst (not shown) in the shift converter 4 can be reduced. Therefore, the cooling structure in the CO selective oxidation reactor 15 and the shift converter 4 can be simplified. This simplification of the cooling structure makes it possible to reduce the volume of the cooling structure, so that the volume of the CO selective oxidation reactor 15 and the shift converter 4 itself can be reduced. It becomes feasible to reduce costs.

  As the control temperature of the CO selective oxidation reactor 15 increases, the reformed gas 8 after the CO selective oxidation reaction is sent to the polymer electrolyte fuel cell 7 downstream of the CO selective oxidation reactor 15. A heat exchanger 31 is provided to lower the temperature before supply. In the heat exchanger 31, a Cu-based CO selective oxidation catalyst 17 on the downstream side of the CO selective oxidation reactor 15 is not present. Thus, the reformed gas 8 that is a fluid (gas) discharged from the CO selective oxidation reactor 15 may be cooled, and thus it is easily cooled using a fluid heat exchanger that is widely used in general. Therefore, the heat exchanger 31 is not required to have a large volume, and the cost is not increased.

  In addition, CuO used as the active metal of the Cu-based CO selective oxidation catalyst 17 does not promote the methanation reaction even in a high temperature range because of its material characteristics. It is possible to eliminate the possibility of an exothermic runaway caused by the occurrence of a methanation reaction, which has been a concern when using an oxidation catalyst, and to improve the controllability of the CO selective oxidation reaction.

  Further, since the CO selective oxidation reaction heat can be recovered with the control temperature of the CO selective oxidation reactor 1 being as high as 150 ° C. to 250 ° C., the cooling supplied to the cooling pipe 21 by the heat of the CO selective oxidation reactor 15 The amount of heat for heating the water 12 to generate the steam 14 used for steam reforming of the hydrocarbon-based fuel 1 in the reformer 2 is 100 due to the use of the noble metal-based CO selective oxidation catalyst. As compared with a conventional CO selective oxidation reactor which has been controlled at a temperature of from 150 ° C. to 150 ° C., it can be recovered efficiently. For this reason, it becomes possible to construct a highly efficient fuel processing apparatus that can efficiently recover the heat generated with the steam reforming process of the hydrocarbon-based fuel 1.

  Next, FIG. 6 shows an apparatus configuration when the Cu-based CO selective oxidation catalyst 17 is applied to the heat transfer fins 37 as another embodiment of the CO selective oxidation reactor of the present invention. It is.

  Specifically, it has a hollow rectangular flat plate shape, and a cooling water inlet 39 is provided in the vicinity of one corner of a pair of diagonals, and a cooling water outlet 40 is provided in the vicinity of the other corner. A cooling pipe 38 is configured so that the cooling water 12 can be circulated. The flat plate-like cooling pipes 38 are arranged in parallel at a required interval (three in the figure), and one of the two opposite sides of the adjacent cooling pipes 38 is formed into a plate-like shape. The two connecting members 41 are connected over the entire length via the connecting members 41 and connect the respective cooling pipes 38 and the adjacent cooling pipes 38 to each other between the adjacent cooling pipes 38. The gas flow path 16 a surrounded by the gas inlet 16 is formed, and one opening is used as the gas inlet 42, and the other opening is used as the gas outlet 43. Furthermore, the direction in which the corrugated plate-like heat transfer fin 37 formed by applying the Cu-based CO selective oxidation catalyst 17 in the gas flow channel 16a is curved in the wave shape of the heat transfer fin 37 is the gas flow channel. The CO selective oxidation reactor 15a is configured by being inserted and arranged so as to be perpendicular to 16a.

When the CO selective oxidation reactor 15a having the above configuration is used, the cooling water inlet 39 and the cooling water outlet 40 of each cooling pipe 38 are connected to the cooling water supply line 22 and the cooling water discharge line similar to those shown in FIG. 23 and connected to the fuel processor shown in FIG. 2 in the same manner as the CO selective oxidation reactor 15 shown in FIG. Thus, the reformed gas 8 produced by steam reforming of the hydrocarbon-based fuel 1 in the reformer 2 and then reduced in CO concentration by the shift reaction in the shift converter 4 is converted into O ₂ or air serving as a combustion support agent. 13 is added to the gas flow path 16a of the CO selective oxidation reactor 15a from the gas inlet 42, the reformed gas 8 is cooled through the cooling pipe 38 in the gas flow path 16a. By contacting with the Cu-based CO selective oxidation catalyst 17 on the surface of the heat transfer fin 37 whose temperature is controlled to be maintained in the active temperature range of 150 ° C. to 250 ° C. by the water 12, it is contained in the reformed gas 8. Since the CO which is selectively reacted with O ₂ is changed to CO ₂ , the CO concentration of the reformed gas 8 is further reduced.

  Accordingly, the present embodiment can provide the same effects as those of the above embodiment.

The present invention is not limited only to the above-described embodiment, and the predetermined content described above is added to the carrier having a composition in which CeO ₂ or CeO ₂ is mixed with Al ₂ O ₃ at the predetermined mixing ratio described above. As long as the Cu-based CO selective oxidation catalyst 17 carrying CuO is exposed in the gas flow paths 16 and 16a through which the reformed gas 8 flows, the CO selective oxidation reactors 15 and 15a are disposed. The cross-sectional area, length, path, and the like of the gas flow paths 16 and 16a may be changed as appropriate, and the shape of the Cu-based CO selective oxidation catalyst 17 may be changed. Further, the Cu-based CO selective oxidation catalyst 17 disposed in the gas flow paths 16 and 16a is cooled so as to be maintained in the predetermined activation temperature range (control temperature of the CO selective oxidation reactors 15 and 15a). If possible, the lengths, shapes, paths, and the like of the cooling pipes 21 and 38 may be changed as appropriate, and the presence / absence, shape, and arrangement of the cooling fins 24 and the heat transfer fins 37 may be freely changed.

  Of course, various modifications can be made without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of a CO selective oxidation method and a CO selective oxidation reactor according to the present invention, in which (a) is a schematic cut side view, and (b) is a schematic cut plan view. It is a schematic diagram which shows the structural example of the fuel processing apparatus which employ | adopted the CO selective oxidation reactor of FIG. It is a figure which shows the result of having investigated the relationship between the catalyst temperature of a Cu type CO selective oxidation catalyst, and CO removal rate about the case where the content of CuO is variously changed. The relationship between the catalyst layer temperature of the Cu-based CO selective oxidation catalyst and the CO reaction rate was examined for various changes in the mixing ratio of Al ₂ O ₃ in the CeO ₂ support of the Cu-based CO selective oxidation catalyst. FIG. It is a figure which shows the result of the reaction stability performance confirmation test of the Cu-type CO selective oxidation catalyst which the present inventors implemented. It is a schematic perspective view which shows the other form of implementation of the CO selective oxidation reactor of this invention. It is a figure which shows the outline | summary of an example of the fuel processing apparatus proposed conventionally.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydrocarbon fuel 7 Solid polymer fuel cell 7a Anode 8 Reformed gas 13 Oxygen or air 15, 15a CO selective oxidation reactor 16, 16a Gas flow path 17 Cu-based CO selective oxidation catalyst 31 Heat exchanger

Claims (9)

  A hydrogen-rich reformed gas obtained by reforming a hydrocarbon fuel is brought into contact with a Cu-based CO selective oxidation catalyst in which copper oxide is supported as an active metal on a cerium oxide support in the presence of a required amount of oxygen. A selective CO oxidation method comprising selectively oxidizing and removing carbon monoxide in the reformed gas.   2. The CO according to claim 1, wherein a carrier obtained by mixing aluminum oxide with cerium oxide at a mixing ratio of 20 mol% or less in terms of mole percentage converted to cerium and aluminum is used as the carrier for the Cu-based CO selective oxidation catalyst. Selective oxidation method.   3. A Cu-based CO selective oxidation catalyst in which copper oxide is supported on a support so as to be 2.0 to 20.0% by weight ratio with respect to the entire catalyst is used as the Cu-based CO selective oxidation catalyst. The CO selective oxidation method as described.   The CO selective oxidation method according to claim 1, 2 or 3, wherein the Cu-based CO selective oxidation catalyst is brought into contact with the reformed gas under a temperature condition of 150 ° C to 250 ° C.   A Cu-based CO selective oxidation catalyst in which copper oxide is supported as an active metal on a cerium oxide support is exposed in a gas flow path for circulating a hydrogen-rich reformed gas obtained by reforming a hydrocarbon-based fuel. A CO selective oxidation reactor, characterized by having a configuration in which it is arranged.   6. The CO selective oxidation reaction according to claim 5, wherein the support of the Cu-based CO selective oxidation catalyst is formed by mixing cerium oxide with aluminum oxide at a mixing ratio of 20 mol% or less in terms of mole percentage converted to cerium and aluminum. vessel.   7. The CO selective oxidation reaction according to claim 5 or 6, wherein the Cu-based CO selective oxidation catalyst is configured such that copper is supported on a support at a weight ratio of 2.0 to 20.0% with respect to the whole catalyst. vessel.   A cooling pipe for cooling the Cu-based CO selective oxidation reactor disposed in the gas flow path is provided, and the Cu-based CO selective oxidation catalyst is cooled to 150 ° C. to 250 ° C. by cooling water flowing through the cooling pipe. The CO selective oxidation reactor according to claim 5, 6 or 7, wherein the temperature can be maintained at the following temperature conditions.   9. The anode inlet side of the polymer electrolyte fuel cell is connected to the outlet side of the gas flow path via a heat exchanger for cooling the temperature of the reformed gas. CO selective oxidation reactor.

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