Fuel reforming catalyst, fuel cell system, method for manufacturing fuel cell cell structure, and fuel reforming method

Abstract

To provide a fuel reforming catalyst capable of obtaining high reforming performance while being low cost without using a noble metal and stably exhibiting performance as a fuel battery, for example, in the case of a structure in which a reforming part is provided in a fuel battery cell unit.SOLUTION: An internal reforming catalyst layer D has a fuel reforming catalyst in which at least nickel and vanadium are supported on a carrier mainly composed of a ceria-based metal oxide or a zirconia-based metal oxide. The internal reforming catalyst layer D is provided within a fuel battery cell unit U.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a fuel reforming catalyst, a fuel cell system including a reforming unit that performs fuel reforming using the fuel reforming catalyst, a fuel cell structure that generates power in this type of fuel cell system, and a method for manufacturing the fuel reforming catalyst and a method for manufacturing the fuel cell structure. [Background technology]

[0002] As a fuel reforming catalyst, a steam reforming catalyst that steam reforms a hydrocarbon fuel is well known. Conventionally, catalysts in which nickel or a precious metal is supported on a support as an active metal have been widely used as such a steam reforming catalyst. For example, Patent Document 1 discloses a steam reforming catalyst in which 10% by weight of nickel and 0.1% by weight of palladium are supported on an inorganic oxide support in which 12% by weight of cerium oxide and 3% by weight of strontium oxide are added to γ-alumina.

[0003] On the other hand, Patent Document 2 proposes a steam reforming catalyst composition containing catalytically active particles that contain a steam reforming catalytically active component and vanadium. This steam reforming catalyst composition is said to be able to suppress deterioration of catalytic performance by adding vanadium to a steam reforming catalytic active component (typically nickel) without reducing the catalytic performance inherent to the steam reforming catalytic active component, and by suppressing sintering during reduction treatment or reforming reaction at temperatures of 500° C. or higher. When the steam reforming catalytic active component is nickel, the proportion of nickel in the composition is relatively high.

[0004] In fuel cell systems, steam reforming catalysts have traditionally been used in "external reformers" that are arranged externally and separately from the fuel cell body. However, Patent Document 3 proposes providing a reforming section within the fuel cell (corresponding to the fuel cell structure of the present invention). Patent Document 3 also discloses providing a nickel-plated layer PR1 as the steam reforming catalyst used in the reforming section (

[0048] ).

[0005] Here, in order to facilitate understanding of the present invention, the terms "fuel cell," "fuel cell structure," and "reforming section" used in this specification will be explained. A fuel cell is a basic unit that is configured by at least forming an anode electrode layer and a cathode electrode layer with an electrolyte layer sandwiched therebetween, and generates electricity between the two electrodes through a cell reaction while a fuel gas (reducing gas) is supplied to the anode electrode layer, and an oxidizing gas containing oxygen is supplied to the cathode electrode layer. The fuel cell structure is a structure that includes the above-mentioned fuel cell and is configured to be able to form a supply path for the fuel gas (reducing gas) and a supply path for the oxidizing gas. The concept includes the fuel cell itself or a support that supports the fuel cell, and the fuel cell unit described below is an example of this fuel cell structure. The reforming section is a section that includes a fuel reforming catalyst and receives a raw fuel gas, such as a hydrocarbon fuel, and produces a reformed gas, which is a gas that contains at least hydrogen, through a catalytic reaction. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2014-184394 A [Patent Document 2] WO2016 / 047504 publication [Patent Document 3] JP 2017-208232 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, the techniques disclosed in the patent documents have the following problems. Patent Document 1 The catalyst described in this patent document is a precious metal catalyst, and therefore has very high activity, but is expensive due to the use of precious metals.

[0008] Patent Document 2 The steam reforming composition described in this patent document uses nickel oxide as a basic material, and therefore uses a large amount of nickel. Furthermore, both (a): vanadium oxide or vanadium-nickel composite oxide, and (b): silicon oxide and zirconia oxide must be present on the surface of the nickel-containing particles. As a result, at least two impregnation steps (a) and (b) are required, which complicates the manufacturing process and increases costs.

[0009] Patent Document 3 The patent document proposes providing a reforming section within the fuel cell structure, but because the nickel is plated, the internal reforming section is essentially a nickel layer, which requires a large amount of nickel. In addition, compatibility between this layer and other parts constituting the fuel cell structure (the support body and fuel cell described in the present invention) is also an issue.

[0010] To summarize, when using a precious metal catalyst, the amount used can be reduced because the catalyst contains precious metals and is highly active, but the cost is high. On the other hand, nickel-based catalysts are less active than precious metal-based catalysts, so in order to obtain a relatively active reforming section, the amount of nickel needs to be increased compared to precious metal-based catalysts. As a result, the cost is about the same as using a precious metal catalyst. Furthermore, the technology of providing a catalyst within a fuel cell structure still requires a large amount of nickel.

[0011] The present invention has been made in consideration of these problems, and its purpose is to obtain a fuel reforming catalyst that can achieve high reforming performance at low cost without using precious metals, and that can stably perform as a fuel cell, even in a structure in which a reforming section is provided within a fuel cell unit, for example. [Means for solving the problem]

[0012] A first characteristic feature of the present invention is that the fuel reforming catalyst comprises at least nickel and vanadium supported on a support mainly composed of a ceria-based metal oxide or a zirconia-based metal oxide.

[0013] Since the fuel reforming catalyst has at least nickel and vanadium supported on a support mainly composed of ceria-based metal oxide or zirconia-based metal oxide, high reforming performance can be obtained even with a small amount of nickel and vanadium supported. In addition, since the support mainly composed of ceria-based metal oxide or zirconia-based metal oxide has a thermal expansion coefficient close to that of other constituent materials used in the fuel cell system, when used in a fuel cell structure, the thermal stress resistance during start-up and stop of the fuel cell structure is improved, making it possible to provide a fuel reforming catalyst with excellent reliability and durability.

[0014] A second characteristic feature of the present invention is that the ratio of the carrier to the entire catalyst is 55% by weight or more. % by weight is synonymous with % by mass. By making the ratio of the carrier to the entire catalyst at least 55% by weight, it becomes possible to support nickel and vanadium as active components in a highly dispersed manner, and while obtaining high fuel reforming performance, the reforming performance can be maintained for a long period of time while suppressing the effects of sintering and the like. In addition, the amount of them used can be reduced to reduce costs. On the other hand, since the ratio of the carrier is high, it is compatible with the structural material in the fuel cell structure (the support referred to in the present application, which will be described later) and the fuel cell provided on the structural material, and when used in a fuel cell unit, it has a thermal expansion coefficient close to that of other structural materials used in the fuel cell system, so that the thermal stress resistance during start-up and stop of the fuel cell structure is improved, and a fuel reforming catalyst with excellent reliability and durability can be obtained. It is more preferable that the ratio of the carrier is 60% by weight or more, and even more preferable that it is 65% by weight or more. This is because it is easier to obtain the above-mentioned effects.

[0015] A third characteristic feature of the present invention is that the ceria-based metal oxide is ceria doped with at least one of gadolinium, samarium, and yttrium.

[0016] This improves material availability because the thermal expansion coefficient is close to that of other constituent materials used in the fuel cell system (especially the fuel cell structure) and the material can be made similar to other materials used in the fuel cell.

[0017] A fourth characteristic feature of the present invention is that the zirconia-based metal oxide is zirconia stabilized with at least one of yttrium and scandium.

[0018] This improves material availability because the thermal expansion coefficient is close to that of other constituent materials used in the fuel cell system (especially the fuel cell structure) and the material can be made similar to other materials used in the fuel cell.

[0019] A fifth characteristic feature of the present invention is that the amount of nickel supported is 0.5% by weight or more.

[0020] If the loading amount is less than 0.5% by weight, it is difficult to obtain catalytic activity contributed by nickel. The loading amount is preferably 1% by weight or more, and good catalytic activity can be obtained. More preferably, it is 5% by weight or more, and sufficient activity can be obtained. On the other hand, it is preferable to set it to less than 35% by weight. This is because if it is loaded more than this amount, it becomes difficult to load nickel highly dispersedly on the carrier, and further improvement of catalytic activity cannot be expected. Also, it is preferably 30% by weight or less, and sufficient catalytic activity can be obtained even at this level. More preferably, it is 25% by weight or less, and the desired fuel reforming performance can be obtained even if the amount of nickel used is limited.

[0021] A sixth characteristic feature of the present invention is that the amount of the vanadium supported is equal to or less than the amount of the nickel supported.

[0022] This is because even with a very small amount of vanadium supported, sufficient reforming performance can be obtained due to the synergistic effect with nickel.

[0023] A seventh characteristic configuration of the present invention is that a fuel cell system includes at least a fuel reforming catalyst having any of the characteristic configurations described thus far, has a reforming section that reforms raw fuel gas into a hydrogen-rich reformed gas by the fuel reforming catalyst, and is equipped with a fuel cell that receives the reformed gas from the reforming section and also receives an oxidizing gas to generate electricity.

[0024] In this way, a fuel cell system can be constructed that is equipped with a reforming section that provides sufficient reforming performance at very low cost.

[0025] An eighth characteristic configuration of the present invention is a fuel cell structure, the fuel cell includes at least an anode electrode layer and a cathode electrode layer sandwiching an electrolyte layer therebetween, a fuel gas supply path that supplies a fuel gas to the anode electrode layer, and an oxidizing gas supply path that supplies an oxidizing gas to the cathode electrode layer; The fuel reforming unit is configured to include, as an internal reforming unit, a reforming unit having at least the fuel reforming catalyst as described above.

[0026] Here, the fuel gas is a reducing gas that can be supplied to the anode electrode layer to generate electricity. In the embodiment described later, when both the external reforming section and the internal reforming section are provided, the raw fuel gas is first supplied to the external reforming section, where a part of the raw fuel gas is reformed to a reformed gas containing hydrogen, and a part of the raw fuel gas remains unreacted and is included in the reformed gas. Then, the reformed gas containing a part of the unreacted raw fuel gas is supplied to the internal reforming section, where the unreacted raw fuel gas is reformed to a reformed gas containing hydrogen, which is supplied to the anode electrode layer as the fuel gas used for generating electricity in the fuel cell. On the other hand, when there is no external reforming section and reforming is performed only in the internal reforming section, the raw fuel gas is supplied to the internal reforming section, where the raw material gas is reformed to a reformed gas containing hydrogen, which is supplied to the anode electrode layer as the fuel gas used for generating electricity in the fuel cell. In addition, when there is no internal reforming section and reforming is performed only in the external reforming section, the raw fuel gas is supplied to the external reforming section, where the raw material gas is reformed into a reformed gas containing hydrogen, and this reformed gas is supplied to the anode electrode layer as the fuel gas used to generate electricity in the fuel cell. By adopting this configuration and providing an internal reforming section integral with the fuel cell, fuel reforming can be performed satisfactorily within the fuel cell structure, and the reformed gas can be obtained to generate electricity, resulting in a compact and highly efficient fuel cell structure.

[0027] A ninth characteristic configuration of the present invention is a fuel cell structure, the fuel cell includes at least an anode electrode layer and a cathode electrode layer sandwiching an electrolyte layer therebetween, a fuel gas supply path that supplies a fuel gas to the anode electrode layer, and an oxidizing gas supply path that supplies an oxidizing gas to the cathode electrode layer; The fuel cell is formed on a support, The fuel reforming device includes a reforming section having at least any one of the fuel reforming catalysts described above as an internal reforming section.

[0028] In this way, it is possible to configure a fuel cell structure that includes an internal reforming section that is inexpensive and provides sufficient reforming performance.

[0029] A tenth characteristic feature of the present invention is that the support is made of a metal.

[0030] In this way, an inexpensive, thin yet strong metal can be used for the support, making it possible to configure an inexpensive, compact fuel cell structure with excellent strength. In particular, if ferritic stainless steel is used as the material for the metal support, the thermal expansion coefficient is close to that of the fuel reforming catalyst carrier, making it possible to configure an inexpensive, compact fuel cell structure with high reliability and durability, such as excellent resistance to heat cycles during start-up and shutdown.

[0031] An eleventh characteristic configuration of the present invention is that the fuel cell is a solid oxide fuel cell.

[0032] In this way, sufficient reforming performance can be obtained at low cost. For example, a fuel reforming catalyst having a carrier with a thermal expansion coefficient close to that of the components constituting the fuel cell or its support can be placed inside the fuel cell structure. This makes it possible to construct a fuel cell structure that is inexpensive, high-performance, and highly reliable and durable, with excellent resistance to heat cycles during start-up and shutdown, or a fuel cell system using the same.

[0033] A twelfth characteristic configuration of the present invention is that it at least comprises an impregnation / supporting step of adding a support mainly composed of a ceria-based metal oxide or a zirconia-based metal oxide to a solution containing at least nickel and vanadium, and impregnating and supporting at least nickel and vanadium on the support.

[0034] In this way, a high-performance fuel reforming catalyst having a small amount of nickel and vanadium supported on a carrier can be produced inexpensively by a simple method.

[0035] In this method for producing a fuel reforming catalyst, the ratio of the carrier to the entire catalyst is preferably adjusted to 55% by weight or more, more preferably 60% by weight or more, and even more preferably 65% ​​by weight or more.

[0036] By producing the fuel reforming catalyst in this manner, it is possible to obtain the functions and effects obtained by adopting the second characteristic configuration of the present invention described above.

[0037] A thirteenth characteristic configuration of the present invention is that, when the fuel reforming catalyst described above is employed in manufacturing the fuel cell structure described above, the impregnated support obtained through an impregnation support process in which the nickel and vanadium are impregnated and supported on the support is placed on at least a part of the support to obtain the reforming section.

[0038] By using such a manufacturing method, the fuel reforming catalyst of the present invention can be placed in a fuel cell unit on a support that supports the fuel cell by a simple technique such as coating, and a reforming section useful for operation as a fuel cell can be formed within the fuel cell structure. The fuel reforming catalyst according to the present invention requires an impregnation support process and a final heat treatment process such as calcination, but this heat treatment process may be performed in conjunction with, before, or after the process of forming the fuel cell that will be provided in the fuel cell structure. In other words, as long as the conditions of the temperature, heating time, etc. in the heat treatment process are the same, the treatments can be performed at the same time. [Brief description of the drawings]

[0039] [Figure 1] FIG. 1 shows a schematic configuration of a fuel cell system. [Diagram 2] A front view and a cross-sectional view of a main part of a fuel cell module [Diagram 3] External view of the fuel cell unit [Figure 4] A diagram showing the manufacturing process of a fuel cell unit. [Diagram 5] An explanatory diagram of the gas reaction system in a fuel cell unit. [Figure 6] Diagram of the internal reforming section [Figure 7] 1 shows the results of Xrd measurement in Example 1 ((a) shows the entire scanned area, and (b) shows a partial scanned area). [Figure 8] 1 shows the results of Xrd measurement in Example 2 ((a) shows the entire scanned area, and (b) shows a partial scanned area). [Figure 9] 1 shows the results of Xrd measurement in Example 3 ((a) shows the entire scanned area, and (b) shows a partial scanned area). [Figure 10] 1 shows the results of Xrd measurement in Example 4 ((a) shows the entire scanned area, and (b) shows a partial scanned area). [Figure 11] Graph showing Xrd measurement results of Reference Example 2 ((a) shows the entire scanned area, and (b) shows a partial scanned area) [Figure 12] 1 shows the results of Xrd measurement in Example 5 ((a) shows the entire scanned area, and (b) shows a partial scanned area). [Figure 13] 1 shows the results of Xrd measurement in Reference Example 7 ((a) shows the entire scanned area, and (b) shows a partial scanned area). [Figure 14] 1 shows the results of Xrd measurement in Example 6 ((a) shows the entire scanned area, and (b) shows a partial scanned area). [Figure 15] FIG. 1 shows the results of Xrd measurement in Reference Example 10 ((a) shows the entire scanned area, and (b) shows a partial scanned area). [Figure 16] 1 shows the results of Xrd measurement in Example 7 ((a) shows the entire scanned area, and (b) shows a partial scanned area). [Figure 17] FIG. 1 shows the results of Xrd measurement in Reference Example 12 ((a) shows the entire scanned area, and (b) shows a partial scanned area). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] The fuel reforming catalyst according to the present invention will be described below in terms of its configuration, preparation method, and fuel reforming performance. The use of this fuel reforming catalyst will also be described with reference to the drawings in relation to the application of the catalyst to a fuel cell system.

[0041] The fuel reforming catalyst of the present invention can be used to reform raw fuel gas in an external reformer 34 (an example of an external reforming section) that is provided independently of the fuel cell module M, which is the main body of the fuel cell, as is conventionally known. It can also be effectively used in a configuration in which an internal reforming catalyst layer D is provided in a fuel cell unit U (an example of a fuel cell structure) that is provided in large numbers within the fuel cell module M (an example of an internal reforming section).

[0042] 1. Fuel reforming catalyst composition The fuel reforming catalyst according to the present invention is constructed by supporting at least nickel and vanadium on a support mainly composed of a ceria-based metal oxide or a zirconia-based metal oxide.

[0043] (Carrier) material When the support is a ceria-based metal oxide, the main component (50% by weight or more) of the support may be cerium oxide (ceria), which may be doped with at least one of gadolinium, samarium, and yttrium. GDC (gadolinium-doped ceria), which will be described later, is an example of a ceria-based metal oxide doped with gadolinium.

[0044] When the support is a zirconia-based metal oxide, it is also preferable that the main component (50% by weight or more) of the support is zirconium oxide (zirconia), and that the zirconia is stabilized with at least one of yttrium and scandium. YSZ (yttria-stabilized zirconia), which will be described later, is an example of a zirconia-based metal oxide in which yttria is dissolved in zirconia to stabilize the fluorite-type crystal structure. Also, a mixture of a ceria-based metal oxide and a zirconia-based metal oxide may be used.

[0045] Percentage of carrier in fuel reforming catalyst The ratio of the carrier to the entire catalyst is preferably adjusted to 55% by weight or more, more preferably 60% by weight or more, and even more preferably 65% ​​by weight or more. In the examples introduced below, the carrier ratio is approximately 70% by weight or more. Therefore, the amount of the main component (mainly nickel) in the catalyst composition disclosed in Patent Document 2 introduced above is different. Furthermore, in the present invention, the support components constituting the fuel reforming catalyst are an issue, and in this regard, as will be explained later, when used in fuel cells, this is closely related to the materials used in the fuel cells.

[0046] (Catalytic active component) As catalytically active components, nickel and vanadium are used together. The amount of nickel supported can be 0.5% by weight or more, preferably 1% by weight or more, more preferably 5% by weight or more, while it is less than 35% by weight, preferably 30% by weight or less, more preferably 25% by weight or less. The amount of vanadium supported is preferably equal to or less than the amount of nickel supported.

[0047] Form of catalytically active component According to the results of a separate X-ray diffraction measurement, nickel and vanadium are believed to exist mainly in the form of nickel oxide and a composite oxide of nickel and vanadium in the fuel reforming catalyst of the present invention after catalyst preparation (without performing reduction treatment before use). The composite oxide of nickel and vanadium is Ni2(V2O7), Ni 1.5 (VO4), Ni3V2O8, Ni3O8V2, (V 1.8 Ni 0.2 )O3 and other composite oxides are thought to be present in a mixed state. Figures 7(a) to 10(a) and Figures 7(b) to 10(b) show the Xrd measurement results for the catalysts of Examples 1 to 4 described below. (a) shows the results for the entire scanning region, and (b) shows the results for a partial scanning region (region where 2θ is 30 to 50 degrees). In these figures, the black circles indicate NiO peaks, the upward black triangles indicate CeO2 peaks, and the downward black triangles are assumed to be the peaks of a composite oxide of nickel and vanadium.

[0048] As the amount of vanadium added increased, the peak intensity of NiO (black circle ●) decreased, and the peak intensity of the downward black triangle assumed to be a composite oxide of nickel and vanadium increased. In addition, in Example 4, which had a large amount of vanadium added, a peak of Ce(VO4) (downward triangle ▽) was shown.

[0049] Figures 11(a) and 11(b) show the Xrd measurement results for the catalyst of Reference Example 2 described below. (a) shows the results for the entire scanning region, and (b) shows the results for a partial scanning region (region where 2θ is 30 to 50 degrees). In these figures, the black circles indicate NiO peaks, and the upward black triangles indicate CeO2 peaks.

[0050] Figures 12(a) and 12(b) show the Xrd measurement results for the catalyst of Example 5 described below. (a) shows the results for the entire scanning region, and (b) shows the results for a partial scanning region (region where 2θ is 30 to 50 degrees). In these figures, the black circles ● indicate the peaks of NiO, the upward black triangles indicate the peaks of GDC, and the downward black triangles indicate the peaks of Ce(VO4), and the downward black triangles are assumed to be the peaks of a composite oxide of nickel and vanadium.

[0051] Figures 13(a) and 13(b) show the Xrd measurement results for the catalyst of Reference Example 7 described below. (a) shows the results for the entire scanning region, and (b) shows the results for a partial scanning region (region where 2θ is 30 to 50 degrees). In these figures, the black circles indicate the peaks of NiO, and the upward black triangles indicate the peaks of GDC.

[0052] Figures 14(a) and 14(b) show the Xrd measurement results for the catalyst of Example 6 described below. (a) shows the results for the entire scanning region, and (b) shows the results for a partial scanning region (region where 2θ is 30 to 50 degrees). In these figures, the black circles indicate NiO peaks, the upward black triangles indicate ZrO2 peaks, and the downward black triangles are assumed to be the peaks of a composite oxide of nickel and vanadium.

[0053] Figures 15(a) and 15(b) show the Xrd measurement results for the catalyst of Reference Example 10 described below. (a) shows the results for the entire scanning region, and (b) shows the results for a partial scanning region (region where 2θ is 30 to 50 degrees). In these figures, the black circles indicate NiO peaks, and the upward black triangles indicate ZrO2 peaks.

[0054] Figures 16(a) and 16(b) show the Xrd measurement results for the catalyst of Example 7 described below. (a) shows the results for the entire scanning region, and (b) shows the results for a partial scanning region (region where 2θ is 30 to 50 degrees). In these figures, the black circles indicate NiO peaks, the upward black triangles indicate YSZ peaks, and the white circles indicate Y2O3 peaks, and the downward black triangles are assumed to be peaks for a composite oxide of nickel and vanadium.

[0055] Figures 17(a) and 17(b) show the Xrd measurement results for the catalyst of Reference Example 12 described below. (a) shows the results for the entire scanning region, and (b) shows the results for a partial scanning region (region where 2θ is 30 to 50 degrees). In these figures, the black circles indicate NiO peaks, and the upward black triangles indicate YSZ peaks.

[0056] When the fuel reforming catalyst of the present invention is subjected to a reduction pretreatment as a pretreatment before being used in a fuel reforming reaction, the above-mentioned oxides are reduced. As a result, NiO is reduced to Ni, and the nickel-vanadium composite oxide is in a state in which the reduction products generated according to the form of each composite oxide are supported on the surface of the support in a highly dispersed manner.

[0057] preparation In preparing the fuel reforming catalyst, the amount of water-soluble nickel compounds (nickel nitrate, nickel chloride, nickel sulfate, nickel ammonium sulfate, nickel nitrate, nickel acetate, nickel oxalate, nickel citrate, etc.) and the amount of water-soluble vanadium compounds (vanadium oxyoxalate, vanadium oxysulfate, vanadium oxydichloride, ammonium vanadate, sodium vanadate, vanadium chloride, vanadium iodide, vanadium bromide, etc.) are determined according to the composition of the target catalyst, and an aqueous solution in which both the nickel compounds and the vanadium compounds are dissolved is obtained. A predetermined amount of carrier powder (ceria, zirconia, GDC, YSZ) is added to the aqueous solution, stirred and impregnated, then evaporated to dryness, dried, crushed, molded, and fired in air. This impregnation is the "impregnation-supporting process" referred to in the present invention, and the resultant product is the "impregnated support." The catalysts in the following examples were prepared using nickel nitrate hexahydrate and vanadium oxyoxalate.

[0058] The above evaporation to dryness, drying and calcination temperatures can be within the commonly used temperature range, but the catalysts in the following examples were prepared at 80°C, 60°C and 800°C, respectively.

[0059] This preparation method is similar not only to the Examples but also to the Comparative Examples and Reference Examples which have different catalytically active components, except that the starting materials are different. An aqueous solution of a compound containing the metal component to be examined is obtained, a carrier is added to the aqueous solution, stirred and impregnated, and then evaporated to dryness and dried, and thereafter, the carrier is pulverized and molded, and then calcined in air to obtain the target product.

[0060] Examples, Reference Examples, and Comparative Examples Tables 1 and 2 show the compositions of the Examples (1 to 7), Reference Examples (1 to 14), and Comparative Examples (1 to 13) that were examined. These tables show the compositions and physical properties of the examples, reference examples and comparative examples, as well as the methane steam reforming performance (methane conversion rate).

[0061] In the table, the catalyst composition is expressed as [active catalyst component / support component]. The active catalyst components are generally listed in the order of first metal (element name) - second metal (element name). However, if the first metal or second metal does not exist, it is not listed. The amount of the first and second metal supported is the amount of metal element obtained by ICP analysis of each prepared catalyst.

[0062] The carriers examined were CeO2 (ceria), ZrO2 (zirconia), GDC (gadolinium-doped ceria), and YSZ (yttria-stabilized zirconia). The amount of gadolinium doped in GDC used in the examples, comparative examples, and reference examples of the present application was about 10% by weight, and the amount of yttria dissolved in YSZ was about 8 mol%.

[0063] The horizontal axis of Table 1 shows the type of support, the amount of the first metal supported (weight %; indicated as wt.% in the table), the amount of the second metal supported (weight %; indicated as wt.% in the table), the amount of CO adsorption (Nml / g), and the BET surface area (m 2 / g). The CO adsorption amount was measured after the catalyst was subjected to a reduction pretreatment in a hydrogen atmosphere at 350° C. for 1 hour.

[0064] As can be seen from this table, the catalytically active components under consideration are nickel (Ni), vanadium (V), cobalt (Co), copper (Cu), iron (Fe), molybdenum (Mo), and tungsten (W).

[0065] Here, the amount of nickel supported as the first metal was about 0.5 to 30% by weight, the amount of vanadium supported as the second metal was about 1 to 10% by weight, and the amount of the second metal supported for comparison was about 3 to 10% by weight, which is the same as the nickel-vanadium combination.

[0066] For comparison, a conventional nickel-supported alumina catalyst (commercially available) was also tested and set as Comparative Example 13.

[0067] [Table 1]

[0068] (Modification activity test) The catalytic activity test was carried out using a fixed-bed flow reactor. The test conditions are as follows. Pretreatment: Before the activity test, reduction pretreatment was carried out in hydrogen at 600°C. Modification activity test Each sample was filled into a reaction tube and incubated with GHSV10000 H -1 Under these conditions, methane and steam were supplied as raw fuel gas, and the temperature of the reaction tube was controlled so that the outlet temperature of the catalyst layer was 600°C to 800°C, to carry out the reforming reaction of the raw fuel gas. The S / C ratio of the gas introduced into the reaction tube [the number of moles of steam / the number of moles of carbon in the raw fuel gas] was 2.5. The composition of the gas discharged from the reaction tube outlet was analyzed by gas chromatography. In the table, the horizontal axis represents temperature, and the results of catalytic activity tests were shown, in which the outlet temperature of the catalyst layer was changed in increments of 50°C from 600°C to 800°C.

[0069] Test results Table 2 shows the methane conversion rate (%) under each test condition. The definition of methane conversion is as follows: (Inlet methane flow rate - outlet methane flow rate) / Inlet methane flow rate x 100

[0070] [Table 2] In the table, "-" indicates that no reforming reaction occurred.

[0071] The above test results revealed the following: 1. In catalysts that support nickel as the first active component and vanadium as the second active component, catalysts that use ceria, GDC, zirconia, or YSZ as the support all show high reforming performance (here, methane conversion rate) that is good for practical use. 2. A catalyst that supports nickel as the first active component and vanadium as the second active component has higher reforming performance than a catalyst that supports only nickel. 3. Among catalysts that support nickel as the first active component and support the second active component, the catalyst that supports vanadium has higher reforming performance than the catalysts that support the other metals examined in this study. 4. In a catalyst that supports nickel as the first active component and vanadium as the second active component, and uses ceria, GDC, zirconia, or YSZ as a support, the amount of supported nickel may be about 0.5 to 30% by weight, and the amount of supported vanadium may be about 1 to 10% by weight. 5. Catalysts in which nickel is supported as the first active component and vanadium is supported as the second active component on ceria, GDC, zirconia, or YSZ supports have higher reforming performance than conventional catalysts in which nickel is supported on alumina.

[0072] From the above, as explained above, it is preferable to employ a fuel reforming catalyst in which at least nickel and vanadium are supported on a carrier mainly composed of a ceria-based metal oxide or a zirconia-based metal oxide.

[0073] The differences from the "steam reforming catalyst composition" disclosed in Patent Document 2 will be explained below. As is clear from paragraphs

[0024] ,

[0038] and

[0039] , this composition has (a) vanadium oxide or vanadium-nickel composite oxide, and (b) both silicon oxide and zirconia oxide present on the surface of nickel-containing particles. Silicon oxide and zirconia oxide are not catalyst carriers, but surface oxides present on the surface of core particles obtained by impregnating vanadium into nickel-containing powder. In other words, it can be said that nickel-containing particles function as a carrier, with (a) impregnated and supported on the surface, and (b) further added to the surface. Moreover, as described in paragraph

[0030] , the content of silicon oxide and zirconia oxide is preferably 2 to 15% by weight relative to 100% by weight of the vanadium-impregnated nickel-containing powder as the core, so silicon oxide and zirconia oxide are clearly not carriers. Also, as described in the same paragraph, silicon oxide and zirconia oxide are described as coatings that cover 20% to 100% of the surface of the vanadium-impregnated nickel-containing powder as the core. Also, it is described that the surface coverage rate may be 100% if there are microcracks. In addition, the production method involves adding nickel hydroxide powder or nickel oxide powder to an aqueous solution of ammonium vanadate, impregnating and adsorbing vanadium, evaporating it to dryness, and calcining the catalyst particles to obtain a catalyst composition. Thus, since the core material of the catalyst composition is nickel hydroxide powder or nickel oxide powder, it is impossible to reduce the amount of nickel used.

[0074] As described in paragraph

[0030] , the content of silicon oxide and zirconia oxide is preferably 2 to 15% by weight relative to 100% by weight of the vanadium-impregnated nickel-containing powder, so that the vanadium-impregnated nickel-containing powder is about 85 to 98% by weight. As described in paragraph

[0023] , vanadium is 1 mol% to 100 mol% relative to 100 mol% of the steam reforming catalytic active component. Considering that the nickel in the catalyst composition is Ni or NiO, it is found from Figures 3 and 4 of the specification that more than half of about 85 to 98% by weight is nickel or nickel oxide, and the Ni content of the catalyst composition is calculated to be at least about 40% by weight. For these reasons, the manufacturing process of the "steam reforming catalyst composition" is complicated and the amount of nickel is large. For these reasons, it is difficult to adopt the composition in the internal reforming section described below.

[0075] 2. Use of fuel reforming catalysts Hereinafter, with reference to Figs. 1 to 6, an embodiment in which the fuel reforming catalyst according to the present invention is used in both the reforming section (the external reformer 34 and the internal reforming catalyst layer D) will be described. The explanation will be given in the order of the overall configuration of the fuel cell system Y, the fuel cell module M which forms the core of the fuel cell system Y, the fuel cell units U which are arranged in large numbers to form the fuel cell module M, and the fuel cells R.

[0076] As described above, in the present invention, the fuel cell unit U is configured to be able to form a fuel cell R supported by a metal support 1 (an example of a support), and gas supply paths (a reducing gas supply path L1 (an example of a fuel gas supply path) and an oxidizing gas supply path L2) provided in the fuel cell unit U. The fuel cell R is configured such that an anode electrode layer A and a cathode electrode layer C are formed with an electrolyte layer B sandwiched therebetween, and the fuel cell unit U is configured such that the fuel cell R is provided on one side of the metal support 1, and an internal reforming catalyst layer D, which is an internal reforming section as the reforming section described up until now, is provided on the other side.

[0077] Fuel Cell System Y As shown in FIG. 1, the fuel cell system Y is configured with a fuel cell module M at its core. This fuel cell module M is equipped with a fuel cell (specifically, a fuel cell R), and generates electricity by receiving a supply of reducing gas (an example of a fuel gas) containing at least hydrogen and an oxidizing gas containing at least oxygen. Power generation is an exothermic reaction under high temperature conditions. As a result, the fuel cell system Y is a so-called "cogeneration system" that can generate and supply both electricity and heat.

[0078] In the fuel cell system Y, the generated power is output via an inverter 38, and heat contained in the exhaust gas is recovered as hot water by a heat exchanger 36. The inverter 38, for example, converts the direct current of the fuel cell module M, converts it to the same voltage and frequency as the power received from a commercial system (not shown), and outputs it. A control unit 39 appropriately controls the inverter 38, and also controls the operation of each device constituting the fuel cell system Y.

[0079] The fuel cell system Y is equipped with a boost pump 30, a desulfurizer 31, a reforming water tank 32, a vaporizer 33, and an external reformer 34 as main devices for supplying reducing gas to a fuel cell module M which is used for generating electricity. The main device for supplying oxidizing gas is a blower 35, which sucks in air and can supply oxidizing gas containing oxygen.

[0080] To further explain the reducing gas supply system, a hydrocarbon-based raw fuel gas (mainly methane) such as city gas is sucked in and pressurized by boost pump 30, and sent to fuel cell module M. Since city gas contains sulfur compound components, these sulfur compound components are removed (desulfurized) in desulfurizer 31. The raw fuel gas is mixed with reforming water supplied from reforming water tank 32 upstream of vaporizer 33, and the water is converted to steam in vaporizer 33.

[0081] The raw fuel gas and steam are sent to the external reformer 34, where the raw fuel gas is steam reformed. This steam reforming reaction is a reaction caused by a reforming catalyst (the fuel reforming catalyst according to the present invention) housed in the reformer, and similarly to the internal reforming reaction described below, a hydrocarbon-based raw fuel gas (e.g., methane, ethane, propane, butane, etc.) is reformed to generate a hydrogen-rich gas (reformed gas) that contains at least hydrogen, which is used for power generation in the fuel cell R. Note that here, some unreacted methane is also contained in the reformed gas.

[0082] Figure 2 shows a front view and a cross-sectional view of the fuel cell module M. As can be seen from Figures 1 and 2, the fuel cell module M in this example is configured in a roughly rectangular shape, and the fuel cell system Y is configured to include this fuel cell module M, an external reformer 34, a vaporizer 33, etc. within a single housing 10.

[0083] In this configuration, the external reformer 34 and vaporizer 33 are located inside the housing 10 that houses the fuel cell module M, making it possible to effectively utilize the heat of the fuel cell module M. That is, the fuel cell module M is provided with a combustion section 101 for exhaust gas containing hydrogen at its upper portion, and this section 101 combusts the remaining combustion components (specifically, hydrogen, carbon monoxide, and methane) contained in the exhaust gas from the fuel cell, and the heat is utilized for steam reforming and vaporization.

[0084] The supply of a reducing gas containing hydrogen and an oxidizing gas containing oxygen to each electrode layer (anode electrode layer A and cathode electrode layer C) provided in the fuel cell unit U or fuel cell R within the casing 10 will be described below.

[0085] Returning to FIG. 1 to explain the outline, a gas manifold 102 is provided downstream of the external reformer 34, and reformed gas containing raw fuel gas is distributed and supplied to a reducing gas supply path L1 provided in the fuel cell unit U, and gas containing hydrogen is supplied to the anode electrode layer A from this supply path L1.

[0086] Meanwhile, oxygen is supplied to the oxidizing gas supply path L2 by sucking air into the casing 10 with a blower 35, and then the oxidizing gas containing the sucked oxygen is supplied to the cathode electrode layer C via the oxidizing gas supply paths L2 provided in the fuel cell units U and the current collector CP (see FIG. 5). In this embodiment, the combustion section 101 is located between the fuel cell module M and the external reformer 34, and therefore the air sucked in by the blower 35 is also used for burning the remaining fuel in the combustion section 101.

[0087] In this way, the exhaust gas generated by the predetermined cell reaction and combustion reaction is sent to the heat exchanger 36 and used for a predetermined heat utilization. Here, the device 103a provided at the exhaust port 103 of the housing 10 is a device for exhaust gas treatment.

[0088] <Fuel cell module M> Fig. 2(a) shows a front view of the fuel cell module M, and Fig. 2(b) shows its cross-sectional view (cross-section II-II in Fig. 2(a)). Furthermore, Fig. 3 shows a perspective view of the fuel cell unit U as viewed from the fuel cell R side, and Fig. 4 shows the manufacturing sequence thereof.

[0089] Here, the fuel cell module M is constructed by stacking a number of fuel cell units U in the horizontal direction (left and right direction in FIG. 2(a)). Specifically, each of these fuel cell units U is configured to be upright mounted on the gas manifold 102 described above. That is, the fuel cell module M is constructed by upright mounting the metal support 1 that supports the fuel cells R on the gas manifold 102.

[0090] 2(b) and 3, the metal support 1 is formed into a cylindrical shape including a reducing gas supply path L1 extending in the vertical direction when the metal support 1 is upright. Meanwhile, a current collector plate CP having an uneven shape is provided in a form electrically connected to the metal support 1, and the current collector plate CP has air permeability, so that the oxidizing gas (specifically, air) sucked into the periphery of the fuel cell module M reaches the cathode electrode layer C of the fuel cell R.

[0091] That is, the fuel cell module M is configured to include a plurality of fuel cell units U, a gas manifold 102, a current collector plate CP, a terminal member 104, and a current draw section 105.

[0092] The fuel cell unit U includes fuel cells R on one surface of a metal support 1, which is a hollow cylinder, and has an overall long, flat plate or rod shape. One longitudinal end of the fuel cell unit U is fixed to a gas manifold 102 by an adhesive member such as a glass sealant. The metal support 1 and the gas manifold 102 are electrically insulated from each other.

[0093] In this way, by stacking multiple fuel cell units U with the back surface of the metal support 1 of one fuel cell unit U in contact with the current collector plate CP of another fuel cell unit U, a predetermined electrical output can be extracted.

[0094] The current collector plate CP is made of a material that is conductive, gas permeable, and elastic in the direction of the stacked parallel arrangement of the fuel cell units U. For example, the current collector plate CP may be made of expanded metal using metal foil, a metal mesh, or a felt-like material. This allows air supplied from the blower 35 to permeate or flow through the current collector plate CP and be supplied to the cathode electrode layer C of the fuel cell R. In the present invention, the flow path through which oxygen-containing gas flows when the fuel cell units U are configured and passes through the current collector plate CP is called the oxidizing gas supply path L2 (see FIG. 5).

[0095] Furthermore, since the collector plate CP has elasticity in the direction of the parallel arrangement of the fuel cell units U, the metal support 1 cantilevered by the gas manifold 102 can also be displaced in the direction of the parallel arrangement, thereby enhancing the robustness of the fuel cell module M against disturbances such as vibration and temperature changes.

[0096] The multiple fuel cell units U arranged in parallel are sandwiched between a pair of end members 104. The end member 104 is a conductive, elastically deformable member, and its lower end is fixed to the gas manifold 102. A current drawing section 105 extending outward along the direction in which the fuel cell units U are arranged in parallel is connected to the end member 104. The current drawing section 105 is connected to the inverter 38, and sends a current generated by power generation by the fuel cell R to the inverter 38.

[0097] <Fuel cell unit U> As explained above, the fuel cell unit U is configured to include a conductive metal support 1 and a fuel cell R, and the fuel cell R is configured to have at least an anode electrode layer A and a cathode electrode layer C sandwiching an electrolyte layer B. The details of the fuel cell R will be described in order below.

[0098] <Metal support 1> 2 and 3, the metal support 1 of this example is configured to include a rectangular flat plate member 72, a U-shaped member 73 having a U-shaped cross section perpendicular to the longitudinal direction, and a lid portion 74. The long sides of the flat plate member 72 and the long sides of the U-shaped member 73 (sides corresponding to the two vertices of the U) are joined, and one end (the upper end side in the illustrated example) is closed by the lid portion 74. This forms the metal support 1 having a space inside and having a flat plate or flat rod shape as a whole. The flat plate member 72 is arranged parallel to the central axis of the metal support 1.

[0099] The internal space of the metal support 1 serves as the reducing gas supply path L1 described above. The lid portion 74 is provided with an exhaust gas outlet 77 through which the gas that has flowed through the reducing gas supply path L1 is discharged to the outside of the metal support 1. The exhaust side (upper side) of this exhaust gas outlet 77 serves as the combustion section 101 described above. The end on the side opposite to the end where the lid portion 74 is provided (the lower side, which is connected to the gas manifold 102 described above) is open and serves as the inlet of the reducing gas supply path L1.

[0100] Materials having excellent electrical conductivity, heat resistance, oxidation resistance, and corrosion resistance are used for the flat plate member 72, the U-shaped member 73, and the cover portion 74. For example, ferritic stainless steel, austenitic stainless steel, nickel-based alloy, etc. are used. In other words, the metal support 1 is constructed to be robust. In particular, ferritic stainless steel is preferably used.

[0101] When ferritic stainless steel is used as the material for the metal support 1, the thermal expansion coefficient is close to that of YSZ (yttria-stabilized zirconia) and GDC (gadolinium-doped ceria, also known as CGO), which are used as materials for the fuel cell R. Therefore, the fuel cell unit U is less likely to be damaged even when temperature cycles of low and high temperatures are repeated. This is preferable because it allows the realization of a fuel cell R with excellent long-term durability. In the present invention, by appropriately selecting materials for the relationship between the fuel cell R and the metal support 1, and for the relationship with the internal reforming section (internal reforming catalyst layer D) described below, the thermal expansion coefficients become close to each other in the same manner as above. As a result, the fuel cell unit U is less likely to be damaged even when a temperature cycle of low and high temperatures is repeated. This makes it possible to realize an internal reforming section with excellent long-term durability.

[0102] The material of the metal support 1 must have a thermal conductivity of 3 Wm -1 K -1 It is preferable to use materials with a resistance of more than 10 Wm -1 K -1 It is even more preferable if the material has a thermal conductivity of 15 to 30 Wm -1 K -1 Therefore, it is suitable as a material for the metal support 1.

[0103] Moreover, it is more preferable that the material of the metal support 1 is a highly tough material that does not cause brittle fracture. Metal materials have higher toughness than ceramic materials and the like, and are therefore suitable for the metal support 1.

[0104] 4, the flat plate member 72 is provided with a plurality of through holes 78 penetrating the front and back surfaces of the flat plate member 72. Gas can flow between the inside and outside of the metal support 1 through these through holes 78. On the other hand, gas cannot flow between the inside and outside of the metal support 1 in the regions of the flat plate member 72 and the U-shaped member 73 where the through holes 78 are not provided.

[0105] As shown in FIG. 5, the fuel cell R is provided on one surface (the front side in FIG. 3, the upper side in FIG. 5) of the metal support 1, and a metal oxide layer x is provided on the surface of the metal support 1 on which the fuel cell R is arranged. By providing the metal oxide layer x in this manner, it is possible to prevent interdiffusion of constituent elements between the metal support 1 and the anode electrode layer A and electrolyte layer B. In other words, the metal oxide layer x acts as a diffusion suppression layer. In this embodiment, three such diffusion suppression layers, x, y, and z, are provided for the fuel cell R. These three layers x, y, and z are shown in FIG. 5.

[0106] <Fuel cell> The fuel cell R is configured with an anode electrode layer A, an electrolyte layer B, a cathode electrode layer C, and appropriate diffusion suppression layers y and z between these layers. This fuel cell R is a solid oxide fuel cell SOFC. The fuel cell R shown as this embodiment is provided with the diffusion suppression layers y and z, so that the electrolyte layer B is indirectly sandwiched between the anode electrode layer A and the cathode electrode layer C. From the viewpoint of generating only cell power generation, it is possible to generate power by forming the anode electrode layer A on one side of the electrolyte layer B and the cathode electrode layer C on the other side. In other words, a fuel cell is formed by having at least these three layers A, B, and C.

[0107] <Anode electrode layer> As shown in FIG. 3, FIG. 5, etc., the anode electrode layer A can be provided in a thin layer state on the front side of the metal support 1 in an area larger than the area where the through-holes 78 are provided. When the anode electrode layer A is provided as a thin layer, the thickness can be, for example, about 1 μm to 100 μm, preferably 5 μm to 50 μm. With such a thickness, it is possible to ensure sufficient electrode performance while reducing the amount of expensive electrode layer material used to reduce costs. The entire area where the through-holes 78 are provided is covered with the anode electrode layer A. That is, the through-holes 78 are formed inside the area where the anode electrode layer A is formed in the metal support 1. In other words, all the through-holes 78 are provided facing the anode electrode layer A.

[0108] The material of the anode electrode layer A can be, for example, a composite material such as NiO-GDC, Ni-GDC, NiO-YSZ, Ni-YSZ, CuO-CeO2, Cu-CeO2, etc. In these examples, GDC, YSZ, and CeO2 can be called aggregates of the composite material. The anode electrode layer A is preferably formed by a low-temperature firing method (for example, a wet method using firing in a low-temperature range without firing in a high-temperature range higher than 1100°C), a spray coating method (such as a thermal spray method, an aerosol deposition method, an aerosol gas deposition method, a powder jet deposition method, a particle jet deposition method, or a cold spray method), a PVD method (such as a sputtering method or a pulsed laser deposition method), or a CVD method. By using these processes that can be used in a low-temperature range, a good anode electrode layer A can be obtained without firing in a high-temperature range higher than 1100°C. Therefore, it is preferable because it is possible to realize an electrochemical element with excellent durability without damaging the metal support 1 and suppressing the interdiffusion of elements between the metal support 1 and the anode electrode layer A. Furthermore, it is even more preferable to use a low-temperature firing method because it makes it easier to handle the raw materials. The amount of Ni contained in the anode electrode layer A can be in the range of 35% by weight or more and 85% by weight or less. The amount of Ni contained in the anode electrode layer A is more preferably more than 40% by weight, and even more preferably more than 45% by weight, since this further enhances the power generation performance. On the other hand, the amount is more preferably 80% by weight or less, since this facilitates cost reduction.

[0109] The anode electrode layer A has a plurality of pores (not shown) in its interior and on its surface to provide gas permeability. That is, the anode electrode layer A is formed as a porous layer. The anode electrode layer A is formed, for example, so that its density is 30% or more and less than 80%. The size of the pores can be appropriately selected so that the electrochemical reaction proceeds smoothly. The density is the proportion of the space occupied by the material constituting the layer, and can be expressed as (1-porosity), and is equivalent to the relative density.

[0110] (Middle class) As shown in FIG. 5, the intermediate layer y can be formed as a thin layer on the anode electrode layer A in a state where the anode electrode layer A is covered. When the intermediate layer y is a thin layer, the thickness can be, for example, about 1 μm to 100 μm, preferably about 2 μm to 50 μm, and more preferably about 4 μm to 25 μm. With such a thickness, it is possible to reduce the amount of expensive intermediate layer material used to reduce costs while ensuring sufficient performance. As the material for the intermediate layer y, for example, YSZ (yttria-stabilized zirconia), ScSZ (scandia-stabilized zirconia), GDC (gadolinium-doped ceria), YDC (yttrium-doped ceria), SDC (samarium-doped ceria), etc. can be used. In particular, ceria-based ceramics are preferably used.

[0111] The intermediate layer y is preferably formed by a low-temperature firing method (for example, a wet method using firing in a low-temperature range without firing in a high-temperature range higher than 1100°C), a spray coating method (such as a thermal spray method, an aerosol deposition method, an aerosol gas deposition method, a powder jet deposition method, a particle jet deposition method, or a cold spray method), a PVD method (such as a sputtering method or a pulsed laser deposition method), or a CVD method. By using these film formation processes that can be used in a low-temperature range, the intermediate layer y can be obtained without firing in a high-temperature range higher than 1100°C. Therefore, the interdiffusion of elements between the metal support 1 and the anode electrode layer A can be suppressed without damaging the metal support 1, and a fuel cell R with excellent durability can be realized. In addition, the low-temperature firing method is more preferable because it makes it easier to handle the raw materials.

[0112] The intermediate layer y has oxygen ion (oxide ion) conductivity. More preferably, it has mixed conductivity of oxygen ions (oxide ions) and electrons. The intermediate layer y having these properties is suitable for application to the fuel cell R.

[0113] (electrolyte layer) The electrolyte layer B is formed in a thin layer state on the intermediate layer y, covering the anode electrode layer A and the intermediate layer y. It can also be formed in a thin film state with a thickness of 10 μm or less. More specifically, the electrolyte layer B is provided across (straddling) the intermediate layer y and the metal support 1, as shown in FIG. 3, FIG. 5, etc. By configuring in this way and joining the electrolyte layer B to the metal support 1, the electrochemical element as a whole can be made to have excellent robustness.

[0114] Furthermore, the electrolyte layer B is provided on the front side of the metal support 1 in an area larger than the area in which the through-hole 78 is provided. In other words, the through-hole 78 is formed inside the area of ​​the metal support 1 in which the electrolyte layer B is formed.

[0115] Additionally, gas leakage from the anode electrode layer A and the intermediate layer y can be suppressed around the electrolyte layer B. More specifically, during power generation, gas is supplied to the anode electrode layer A from the back side of the metal support 1 through the through-holes 78. In the area where the electrolyte layer B contacts the metal support 1, gas leakage can be suppressed without providing a separate member such as a gasket. Note that, although the electrolyte layer B covers the entire periphery of the anode electrode layer A in this embodiment, a configuration in which the electrolyte layer B is provided on the top of the anode electrode layer A and the intermediate layer y and a gasket or the like is provided around the periphery may also be used.

[0116] As the material of the electrolyte layer B, YSZ (yttria-stabilized zirconia), ScSZ (scandia-stabilized zirconia), GDC (gadolinium-doped ceria), YDC (yttrium-doped ceria), SDC (samarium-doped ceria), LSGM (strontium-magnesium-doped lanthanum gallate), etc. can be used. In particular, zirconia-based ceramics are preferably used. When the electrolyte layer B is made of zirconia-based ceramics, the operating temperature of the SOFC using the fuel cell R can be made higher than that of ceria-based ceramics. In the case of SOFC, a material that can exhibit high electrolyte performance even in a high temperature range of about 650°C or higher such as YSZ is used as the material of the electrolyte layer B, and a hydrocarbon-based raw fuel such as city gas or LPG is used as the raw fuel gas of the system, and the raw fuel gas is converted into reducing gas for the SOFC by steam reforming or the like, and then a highly efficient SOFC system can be constructed in which the heat generated in the cell stack of the SOFC is used to reform the raw fuel gas.

[0117] The electrolyte layer B is preferably formed by a low-temperature firing method (for example, a wet method using firing in a low-temperature range without firing in a high-temperature range exceeding 1100°C), a spray coating method (such as a thermal spray method, an aerosol deposition method, an aerosol gas deposition method, a powder jet deposition method, a particle jet deposition method, or a cold spray method), a PVD method (such as a sputtering method or a pulse laser deposition method), or a CVD method. By using these film formation processes that can be used in a low-temperature range, a dense electrolyte layer B with high airtightness and gas barrier properties can be obtained without firing in a high-temperature range exceeding 1100°C. Therefore, damage to the metal support 1 can be suppressed, and the interdiffusion of elements between the metal support 1 and the anode electrode layer A can be suppressed, and a fuel cell R with excellent performance and durability can be realized. In particular, the low-temperature firing method or the spray coating method is preferable because it can realize a low-cost element. Furthermore, the spray coating method is even more preferable because it is easy to obtain a dense electrolyte layer with high airtightness and gas barrier properties in a low-temperature range.

[0118] The electrolyte layer B is densely configured to prevent leakage of reducing gas and oxidizing gas and to exhibit high ion conductivity. The density of the electrolyte layer B is preferably 90% or more. It is more preferable that the density is 95% or more, and even more preferable that the density is 98% or more. When the electrolyte layer B is a uniform layer, it is preferable that the density is 95% or more, and more preferable that the density is 98% or more. When the electrolyte layer B is configured in a multi-layered form, it is preferable that at least a part of the electrolyte layer B includes a layer (a dense electrolyte layer) having a density of 98% or more, and more preferable that the electrolyte layer B includes a layer (a dense electrolyte layer) having a density of 99% or more. When such a dense electrolyte layer is included in a part of the electrolyte layer, it is easy to form an electrolyte layer that is dense and has high airtightness and gas barrier properties, even when the electrolyte layer is configured in a multi-layered form.

[0119] (Reaction prevention layer) The reaction prevention layer z can be formed in a thin layer state on the electrolyte layer B. When the layer is a thin layer, the thickness can be, for example, about 1 μm to 100 μm, preferably about 2 μm to 50 μm, and more preferably about 3 μm to 15 μm. With such a thickness, it is possible to reduce the amount of expensive reaction prevention layer material used to reduce costs while ensuring sufficient performance. The material of the reaction prevention layer z may be any material that can prevent the reaction between the components of the electrolyte layer B and the components of the cathode electrode layer C, and for example, a ceria-based material is used. In addition, a material containing at least one element selected from the group consisting of Sm, Gd, and Y is preferably used as the material of the reaction prevention layer z. It is preferable that the material contains at least one element selected from the group consisting of Sm, Gd, and Y, and the total content of these elements is 1.0% by weight or more and 10% by weight or less. By introducing the reaction prevention layer z between the electrolyte layer B and the cathode electrode layer C, the reaction between the constituent material of the cathode electrode layer C and the constituent material of the electrolyte layer B is effectively suppressed (diffusion suppression), and the long-term stability of the performance of the fuel cell R can be improved. The reaction prevention layer z is preferably formed by using a method that can be used at a processing temperature of 1100°C or less, since this can suppress damage to the metal support 1 and also suppress interdiffusion of elements between the metal support 1 and the anode electrode layer A, thereby realizing a fuel cell R with excellent performance and durability. For example, the reaction prevention layer z can be formed by using a low-temperature firing method (for example, a wet method that uses a firing process in a low-temperature range that does not include a firing process in a high-temperature range exceeding 1100°C), a spray coating method (such as a thermal spray method, an aerosol deposition method, an aerosol gas deposition method, a powder jet deposition method, a particle jet deposition method, or a cold spray method), a PVD method (such as a sputtering method or a pulsed laser deposition method), or a CVD method. In particular, low-temperature firing or spray coating is preferable because it allows low-cost devices to be realized. Furthermore, low-temperature firing is even more preferable because it allows easy handling of raw materials.

[0120] (Cathode electrode layer) The cathode electrode layer C can be formed in a thin layer state on the electrolyte layer B or the reaction prevention layer z. When the cathode electrode layer C is formed as a thin layer, the thickness can be, for example, about 1 μm to 100 μm, preferably 5 μm to 50 μm. With such a thickness, it is possible to reduce the amount of expensive cathode electrode layer material used to reduce costs while ensuring sufficient electrode performance. As the material for the cathode electrode layer C, for example, composite oxides such as LSCF and LSM, ceria-based oxides, and mixtures thereof can be used. In particular, it is preferable that the cathode electrode layer C contains a perovskite-type oxide containing two or more elements selected from the group consisting of La, Sr, Sm, Mn, Co, and Fe. The cathode electrode layer C formed using the above materials functions as a cathode.

[0121] In addition, the cathode electrode layer C is preferably formed by appropriately using a method that can form the cathode electrode layer C at a processing temperature of 1100°C or less, since damage to the metal support 1 can be suppressed, and the interdiffusion of elements between the metal support 1 and the anode electrode layer A can be suppressed, and a fuel cell R with excellent performance and durability can be realized. For example, a low-temperature firing method (for example, a wet method using a firing process in a low-temperature range that does not involve firing at a high temperature range exceeding 1100°C), a spray coating method (a method such as a thermal spraying method, an aerosol deposition method, an aerosol gas deposition method, a powder jet deposition method, a particle jet deposition method, or a cold spray method), a PDV method (a sputtering method, a pulsed laser deposition method, or the like), a CVD method, or the like can be appropriately used. In particular, the low-temperature firing method or the spray coating method is preferable because it allows a low-cost element to be realized. Furthermore, the low-temperature firing method is even more preferable because it makes it easier to handle the raw materials.

[0122] The above has been an explanation of the basic configuration of the fuel cell, and below, the characteristic configuration of the fuel cell unit U of this embodiment will be explained mainly with reference to Figs. As described above, in this embodiment, the reducing gas supply path L1 is formed in the metal support 1 as a fuel gas supply path that supplies a fuel gas containing hydrogen to the anode electrode layer A. As shown by the dashed line arrow in FIG. 3, the gas in this supply path L1 flows in one direction from the axial opening side (lower side) of the metal support 1 to the axial cover part side (upper side). Hydrogen H2 for the power generation reaction can be supplied to the anode electrode layer A through the through hole 78 provided penetrating the front and back of the flat plate member 72. Here, the power generation reaction in the fuel cell R is a known cell reaction, and moisture (water vapor) H2O is discharged from the anode electrode layer A to the through hole 78 along with this reaction. As a result, the reducing gas supply path L1 of the present invention serves as a supply part L3b that supplies a gas containing hydrogen H2, and at the same time, is accompanied by a discharge part L3a for moisture (water vapor) H2O.

[0123] Therefore, as shown in Figure 2(b) and Figure 5, an internal reforming catalyst layer D is provided on the inner surface of the metal support 1. The fuel reforming catalyst unique to the present invention described above is applied to the inner surface.

[0124] In addition to hydrogen obtained by external reforming, the reducing gas supply path L1 also flows pre-reformed gas (raw fuel gas, specifically methane CH4) to be reformed. The moisture (steam) H2O generated in the anode electrode layer A is returned to the internal reforming catalyst layer D to perform steam reforming, and hydrogen H2 is supplied to the anode electrode layer A from the through-hole 78 located downstream (the back side of the paper in the case of FIG. 5) to generate power. Therefore, the internal reformed fuel supply path L3 is configured to include a discharge part L3a for the generated steam H2O and a supply part L3b for the internally reformed hydrogen H2. The discharge part L3a is configured to also function as the supply part L3b, and the supply part L3b also functions as the discharge part L3a.

[0125] The fuel reforming catalyst according to the present invention described above is used as the material for the internal reforming catalyst layer D. That is, it is disposed at a portion that will become the internal reforming catalyst layer D. This catalyst has a relatively high specific surface area and is in an air permeable state.

[0126] The internal reforming catalyst layer D is preferably formed by a low-temperature firing method (for example, a wet method using a firing process in a low-temperature range that does not involve firing at a high temperature range higher than 1100°C). For example, the internal reforming catalyst layer D can be formed by mixing the fuel reforming catalyst powder according to the present invention with an organic dispersion medium, applying the obtained slurry to a desired location, and firing the slurry. This is because a process that can be used in a low-temperature range can form a good internal reforming catalyst layer D while suppressing damage caused by high-temperature heating of the reducing gas supply path L1 in which the internal reforming catalyst layer D is provided, thereby realizing a fuel cell unit U with excellent durability. In addition, it is preferable to form the internal reforming catalyst layer D after forming the diffusion suppression layer x on the surface of the metal support 1, since this can suppress the scattering of Cr from the metal support 1.

[0127] The thickness of such an internal reforming catalyst layer D is preferably, for example, 1 μm or more, more preferably 2 μm or more, and even more preferably 5 μm or more. This is because such a thickness increases the contact area with the fuel gas and water vapor, thereby increasing the internal reforming rate. Also, the thickness is preferably, for example, 500 μm or less, more preferably 300 μm or less, and even more preferably 100 μm or less. By making the thickness in this range, the amount of expensive internal reforming catalyst material used can be reduced, thereby reducing costs.

[0128] 5 again, a brief explanation will be given of the steam reforming reaction in this internal reforming catalyst layer D. As shown in the figure, by providing an internal reforming catalyst layer D in a fuel cell unit U, methane CH4, which is the raw fuel gas supplied to the reducing gas supply path L1, can be reformed as follows to produce hydrogen H2 and carbon monoxide CO, which serve as fuel gas.

[0129] [C1] CH4+H2O→CO+3H2 [Cation 2] CO+H2O→CO2+H2 [C3] CH4+2H2O→CO2+4H2

[0130] The temperature of this reducing gas supply path L1 (internal reforming catalyst layer D) is, in effect, 600°C to 900°C, which is the operating temperature of the fuel cell R (SOFC operating temperature). The functional configuration of the fuel cell unit U of the embodiments described thus far as a fuel cell is diagrammed in FIG. 6(a).

[0131] By adopting such a structure, water (water vapor) H2O discharged from the anode electrode layer A can be used to cause steam reforming within the metal support 1, and the hydrogen H2 and carbon monoxide CO obtained by the reforming can be supplied to the anode electrode layer A and used as fuel gas for power generation.

[0132] [Another embodiment] (1) In the above embodiment, an example was shown in which the fuel cell unit U includes a metal support 1, which supports the fuel cell R and forms the gas supply paths L1, L2. The fuel reforming catalyst according to the present invention is disposed in the reducing gas supply path L1, and fuel reforming is carried out within a structure in which the fuel cell R is integrated. However, in the operation of a fuel cell, it is sufficient to supply the gases required for power generation to each electrode, and in some cases the fuel cell itself is made to be self-supporting and is configured with each supply path. In such a configuration, the fuel cell itself or an integrated portion thereof may be provided with the fuel reforming catalyst according to the present invention, and reforming of the raw fuel gas may be carried out at that site. Therefore, in the present invention, the reforming section provided as a structure integral with the fuel cell R is called an internal reforming section, and the structure is called a fuel cell structure.

[0133] (2) In the above embodiment, an example was shown in which the fuel reforming catalyst of the present invention is used in both the external reforming section (specifically, the external reformer 34) and the internal reforming section (specifically, the internal reforming catalyst layer D), which serve as the reforming sections in the fuel cell system Y. However, the fuel cell system Y may be configured to include either an external reforming section or an internal reforming section as long as it is capable of supplying the reducing gas required for the fuel cell (the reformed gas that serves as the fuel gas) in an amount commensurate with the power generation. 1.External modification When only an external reforming section is provided, almost all of the raw fuel gas is reformed and the reformed gas is supplied to the fuel cell units U as fuel gas. 2. Internal modification In the case where only an internal reforming section is provided, reforming of the raw fuel gas is carried out within the fuel cell structure while supplying raw fuel gas and water vapor to the reducing gas supply path L1, and the hydrogen-rich reformed gas reaches the anode electrode layer A side of the fuel cell R as fuel gas. Furthermore, as explained above, when attempting to utilize the moisture (water vapor) generated by the power generation reaction of the fuel cell for reforming downstream in the flow direction of the reducing gas (fuel gas), the configuration is as shown in Figures 6(a) and (b).

[0134] (3) In the above embodiment, an example has been shown in which the fuel reforming catalyst according to the present invention is disposed (an internal reforming section is provided) within the fuel cell unit U, over the entire area of ​​the reducing gas supply channel L1 in the metal support 1. As explained above, Fig. 6(a) is a schematic diagram showing this structure. On the other hand, when the reforming section is provided within the fuel cell unit U, the amount of catalyst used can be reduced by limiting the position where the fuel reforming catalyst according to the present invention is arranged, thereby reducing costs. That is, when using water vapor generated with power generation in the fuel cell for reforming, the catalyst may be provided only at a position downstream of the most upstream through-hole 78 in the reducing gas supply passage L1, as shown in Fig. 6(b). With this configuration, the amount of valuable fuel reforming catalyst can be reduced.

[0135] In addition, in the example shown in Figures 6(a) and (b), an example is shown in which water vapor generated by the fuel cell generating electricity is used for reforming, but a structure in which fuel reforming is performed using only water vapor coexisting with the raw fuel gas supplied to the fuel cell unit U or the reformed gas containing the raw fuel gas (only water vapor supplied from the outside) instead of this water vapor may be used. That is, a reforming section (internal reforming catalyst layer D) in which a fuel reforming catalyst is arranged on the upstream side of the reducing gas supply path L1 is provided for the fuel cell R, and the reformed gas is supplied from the reforming section to the fuel cell R, and the gas discharged from the fuel cell R may be discharged separately and independently. An example of such a configuration is shown in FIG. 6(c).

[0136] (4) The above (3) is a schematic example of the case where an internal reforming section is provided. In the example shown in Figures 2 to 4, an example is shown in which the reforming section is provided around the entire circumference of the cross section of the reducing gas supply path L1 formed inside the metal support 1. However, this reforming section need only be provided at a position where it can come into contact with the gas flowing through the reducing gas supply path L1, and it may be provided only on the surface opposite to the surface on which the fuel cell R is formed, or only on the surface facing the opposite surface.

[0137] (5) Furthermore, the site to be the internally modified portion may be the inner surface of the through hole 78 formed in the metal support 1 .

[0138] (6) In the above embodiment, an example was shown in which a metal support 1 was used in the fuel cell unit U, but the support may be made of a material other than metal, such as ceramic. Therefore, the structure that supports the fuel cell R in the fuel cell structure is simply called the support.

[0139] (7) In the above embodiment, an example was shown in which a powdered carrier was used. However, the fuel reforming catalyst according to the present invention can also be obtained by adding a carrier formed to a certain size (for example, a sphere having a diameter of several mm) to an aqueous solution containing nickel and vanadium components to impregnate and support the carrier, and then carrying out steps such as drying and calcination as necessary.

[0140] (8) In the above embodiment, an example was shown in which a hydrocarbon gas such as methane, ethane, propane, or butane was used as the raw fuel. However, the fuel reforming catalyst according to the present invention can also be used as a fuel reforming catalyst when reforming raw fuels such as hydrocarbons such as natural gas, naphtha, or kerosene, alcohols such as methanol or ethanol, or ethers such as DME.

[0141] (9) In the above embodiments, examples have been shown in which the fuel reforming catalyst of the present invention is used in a solid oxide fuel cell system or fuel cell cell structure, but the fuel reforming catalyst of the present invention can also be used in the external reforming section of a fuel cell system that uses fuel cells other than solid oxide fuel cells, such as solid polymer fuel cells, phosphoric acid fuel cells, or molten carbonate fuel cells, and the fuel reforming catalyst of the present invention can also be used in fuel cell cell structures other than solid oxide fuel cells, such as molten carbonate fuel cells.

[0142] (10) In the above embodiment, an example was shown in which the fuel reforming catalyst of the present invention is used for a steam reforming reaction of methane. However, the fuel reforming catalyst of the present invention can also be used for partial combustion (oxidation) reforming reactions and dry reforming reactions other than steam reforming reactions, as well as fuel reforming reactions that combine these fuel reforming reactions. [Explanation of symbols]

[0143] 1 Metal support (support) 34 External reformer (external reforming section; reforming section) A Anode electrode B electrolyte layer C cathode electrode D Internal reforming catalyst layer (internal reforming section; reforming section) L1 Reducing gas supply path (fuel gas supply path) L2 Oxidizing gas supply line R Fuel cell U Fuel cell unit (fuel cell structure) Y Fuel Cell System

Claims

1. A method for producing a fuel reforming catalyst, comprising: adding a carrier mainly composed of a ceria-based metal oxide or a zirconia-based metal oxide to a solution containing at least nickel and vanadium; at least going through an impregnation / support step in which at least nickel and vanadium are impregnated and supported on the carrier; obtaining a fuel reforming catalyst in which at least nickel and vanadium are supported on the carrier; and performing a reduction pretreatment on the fuel reforming catalyst to produce a fuel reforming catalyst having a CO adsorption amount of 0.17 to 0.68 Nml / g.

2. 2. The method for producing a fuel reforming catalyst according to claim 1, wherein the ratio of the support to the entire catalyst is 55% by weight or more.

3. 3. The method for producing a fuel reforming catalyst according to claim 1, wherein the zirconia-based metal oxide is zirconia stabilized with at least one of yttrium and scandium.

4. The method for producing a fuel reforming catalyst according to any one of claims 1 to 3, wherein the amount of nickel supported is 0.5% by weight or more.

5. The method for producing a fuel reforming catalyst according to any one of claims 1 to 4, wherein the amount of the vanadium supported is equal to or less than the amount of the nickel supported.

6. A method for producing a fuel cell system comprising: at least a fuel reforming catalyst produced by the method for producing a fuel reforming catalyst according to any one of claims 1 to 5; a reforming section that reforms a raw fuel gas into a hydrogen-rich reformed gas by the fuel reforming catalyst; and a fuel cell that receives the reformed gas from the reforming section and an oxidizing gas to generate electricity.

7. the fuel cell includes at least an anode electrode layer and a cathode electrode layer sandwiching an electrolyte layer therebetween, a fuel gas supply path that supplies a fuel gas to the anode electrode layer, and an oxidizing gas supply path that supplies an oxidizing gas to the cathode electrode layer; A method for producing a fuel cell structure comprising, as an internal reforming section, a reforming section comprising at least a fuel reforming catalyst produced by the method for producing a fuel reforming catalyst according to any one of claims 1 to 5.

8. the fuel cell includes at least an anode electrode layer and a cathode electrode layer sandwiching an electrolyte layer therebetween, a fuel gas supply path that supplies a fuel gas to the anode electrode layer, and an oxidizing gas supply path that supplies an oxidizing gas to the cathode electrode layer; The fuel cell is formed on a support, A method for producing a fuel cell structure comprising, as an internal reforming section, a reforming section comprising at least a fuel reforming catalyst produced by the method for producing a fuel reforming catalyst according to any one of claims 1 to 5.

9. The method for producing a fuel cell structure according to claim 8 , wherein the support is made of a metal.

10. The method for producing a fuel cell structure according to any one of claims 7 to 9, wherein the fuel cell is a solid oxide fuel cell.

11. A fuel reforming catalyst is obtained by at least carrying out an impregnation supporting step of adding a carrier mainly composed of a ceria-based metal oxide or a zirconia-based metal oxide to a solution containing at least nickel and vanadium, and impregnating and supporting at least nickel and vanadium on the carrier, and A fuel reforming method in which the fuel reforming catalyst is pretreated by hydrogen reduction and then contacted with a raw fuel gas containing methane and water vapor at 600° C. to 650° C. to reform the fuel.

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