Patent Description:
Hydrogen (H<NUM>) to be used as a fuel in an anode of a fuel cell is obtained through steam reforming from a hydrocarbon-based fuel such as liquefied natural gas (LNG), liquefied petroleum gas (LPG), naphtha, gasoline, kerosene, or light diesel oil, an alcohol-based fuel such as methanol, or city gas.

A reformed gas obtained through the steam reforming contains, in addition to hydrogen, carbon monoxide (CO) at a significant concentration. The CO contained in the reformed gas causes various problems in the fuel cell. Accordingly, it is necessary to decrease the carbon monoxide concentration in the reformed gas as much as possible before the reformed gas is supplied to the fuel cell.

To that end, hitherto, as one of the methods of decreasing the CO concentration, there has been proposed a method involving converting carbon monoxide into methane (methanation of carbon monoxide) (for example, Patent Literatures <NUM> to <NUM>). <CIT> discloses a method of methanation reaction of carbon monoxide using a catalyst containing Ru and Fe supported on a carbon support (activated carbon).

However, the activity of the related-art catalyst for methanation is not necessarily sufficient.

The present invention has been made in view of the problem, and one of the objects of the present invention is to achieve effective methanation of carbon monoxide.

Disclosure which does not fall within the scope of the claims is presented for illustrative purpose.

A support for supporting a metal disclosed herein includes a carbonized material obtained by carbonizing raw materials containing an organic substance and a metal, in which the support is used for supporting a metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide.

In addition, in the support for supporting a metal, the metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide may include one or more kinds selected from the group consisting of Ni, Ru, Rh, Pd, Pt, Ir, Cu, W, Cs, K, Na, Co, Fe, Ca, Mg, Ba, Sr, and Li. In this case, the metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide may include Ni.

In addition, the support for supporting a metal, when supporting Ni, has: a ratio of a peak area in a range of from more than <NUM> eV to <NUM> eV or less to a peak area in a range of from <NUM> eV or more to <NUM> eV or less of <NUM> or more, the peak areas being obtained by XPS measurement of an electron state of 2p orbitals of the Ni; and a molar ratio of an H<NUM> desorption amount in a range of from <NUM> to <NUM>, which is obtained by an H<NUM> temperature-programmed desorption method, to a CO desorption amount in a range of from <NUM> to <NUM>, which is obtained by a CO temperature-programmed desorption method, of <NUM> or more.

A metal-supported catalyst disclosed herein includes: a support formed of a carbonized material obtained by carbonizing raw materials containing an organic substance and a metal; and a metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide, the metal being supported on the support.

In addition, in the metal-supported catalyst, the metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide may include one or more kinds selected from the group consisting of Ni, Ru, Rh, Pd, Pt, Ir, Cu, W, Cs, K, Na, Co, Fe, Ca, Mg, Ba, Sr, and Li. In this case, the metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide may include Ni.

In addition, the metal-supported catalyst has: a ratio of a peak area in a range of from more than <NUM> eV to <NUM> eV or less to a peak area in a range of from <NUM> eV or more to <NUM> eV or less of <NUM> or more, the peak areas being obtained by XPS measurement of an electron state of 2p orbitals of the Ni; and a molar ratio of an H<NUM> desorption amount in a range of from <NUM> to <NUM>, which is obtained by an H<NUM> temperature-programmed desorption method, to a CO desorption amount in a range of from <NUM> to <NUM>, which is obtained by a CO temperature-programmed desorption method, of <NUM> or more.

A methanation reaction apparatus disclosed herein includes any one of the metal-supported catalysts, in which the methanation reaction apparatus is used for a methanation reaction of carbon monoxide.

A method disclosed herein includes using, as a support for supporting a metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide, a carbonized material obtained by carbonizing raw materials containing an organic substance and a metal.

In addition, in the method, the metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide may include one or more kinds selected from the group consisting of Ni, Ru, Rh, Pd, Pt, Ir, Cu, W, Cs, K, Na, Co, Fe, Ca, Mg, Ba, Sr, and Li. In this case, the metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide may include Ni.

A method disclosed herein includes performing a methanation reaction of carbon monoxide using any one of the metal-supported catalysts.

In addition, the method may include treating a first gas containing carbon monoxide to produce a second gas whose concentration of carbon monoxide is decreased compared to that of the first gas. In this case, the first gas and the second gas may each further contain hydrogen. In addition, the method may use a methanation reaction apparatus including the metal-supported catalyst.

A method disclosed herein is a method of selecting, from a plurality of candidate supports, a support for supporting a metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide, the method including: determining, for each of the plurality of candidate supports in a state of supporting Ni, whether or not a ratio of a peak area in a range of from more than <NUM> eV to <NUM> eV or less to a peak area in a range of from <NUM> eV or more to <NUM> eV or less, the peak areas being obtained by XPS measurement of an electron state of 2p orbitals of the Ni, is equal to or higher than a threshold set in advance of <NUM> or more; determining, for each of the plurality of candidate supports in a state of supporting Ni, whether or not a molar ratio of an H<NUM> desorption amount in a range of from <NUM> to <NUM>, which is obtained by an H<NUM> temperature-programmed desorption method, to a CO desorption amount in a range of from <NUM> to <NUM>, which is obtained by a CO temperature-programmed desorption method, is equal to or higher than a threshold set in advance of <NUM> or more; and selecting, from the plurality of candidate supports, a support for which it is determined that the ratio of the peak areas is equal to or higher than the threshold, and the molar ratio is equal to or higher than the threshold.

According to the present invention, effective methanation of carbon monoxide are provided.

Hereinafter, embodiments of the present invention are described. It should be noted that the present invention is not limited to examples shown in these embodiments.

A support for supporting a metal as disclosed herein is a support formed of a carbonized material obtainedby carbonizing raw materials containing an organic substance and a metal, the support being used for supporting a metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide. That is, the carbonized material constituting the support is obtained by carbonizing the raw materials containing the organic substance and the metal.

The organic substance contained in the raw materials is not particularly limited as long as the organic substance can be carbonized. That is, as the organic substance, for example, there may be used a high-molecular-weight organic compound (for example, a resin such as a thermosetting resin and/or a thermoplastic resin) and/or a low-molecular-weight organic compound. In addition, biomass may also be used as the organic substance.

The organic substance may be a nitrogen-containing organic substance. The nitrogen-containing organic substance is not particularly limited as long as it is an organic substance containing an organic compound containing in its molecule a nitrogen atom, and any one or more kinds of nitrogen-containing organic substances may be used.

The organic substance may contain a ligand capable of coordinating with a metal. The ligand is, for example, a compound containing in its molecule one or more ligand atoms. Examples of the ligand atom may include one or more kinds selected from a group consisting of a nitrogen atom, a phosphorous atom, an oxygen atom, and a sulfur atom. In addition, an example of the ligand is a compound having one or a plurality of ligand groups in its molecule. Examples of the ligand group may include one or more kinds selected from a group consisting of an amino group, a phosphino group, a carboxyl group, and a thiol group.

As the organic substance, there may be used, for example, one or more kinds selected from a group consisting of a phenol resin, polyfurfuryl alcohol, furan, a furan resin, a phenol formamide resin, melamine, a melamine resin, an epoxy resin, a chelate resin, a polyamide imide resin, pyrrole, polypyrrole, polyvinyl pyrrole, <NUM>-methyl polypyrrole, acrylonitrile, polyacrylonitrile, a polyacrylonitrile-polymethacrylic acid copolymer, polyvinylidene chloride, thiophene, oxazole, thiazole, pyrazole, vinylpyridine, polyvinylpyridine, pyridazine, pyrimidine, piperazine, pyran, morpholine, imidazole, <NUM>-methylimidazole, <NUM>-methylimidazole, quinoxaline, aniline, polyaniline, succinic acid dihydrazide, adipic acid dihydrazide, polysulfone, polyaminobismaleimide, polyimide, polyvinyl alcohol, polyvinyl butyral, benzimidazole, polybenzimidazole, polyamide, polyester, polylactate, polyether, polyether ether ketone, cellulose, carboxymethylcellulose, lignin, chitin, chitosan, pitch, lignite, silk , wool, polyamino acid, a nucleic acid, DNA, RNA, hydrazine, a hydrazide, urea, salen, polycarbazole, polybismaleimide, triazine, polyacrylic acid, polyacrylate, polymethacrylate, polymethacrylic acid, polyurethane, polyamide amine, and polycarbodiimide.

The metal contained in the raw materials is Co.

As the metal, there may be used an elementary substance of the metal or a compound of the metal. As the metal compound, for example, one or more kinds selected from a group consisting of a metal salt, a metal oxide, a metal hydroxide, a metal nitride, a metal sulfide, a metal carbide, and a metal complex may be used, and one or more kinds selected from the group consisting of a metal salt, a metal oxide, a metal sulfide, and a metal complex may be preferably used. It should be noted that when the organic substance described above contains a ligand, a metal complex is formed in the raw materials.

The amount of the metal contained in the rawmaterials is not particularly limited, and for example, the weight ratio of the metal to the organic substance contained in the raw materials may be <NUM> to <NUM> wt%.

The raw materials are prepared by mixing the organic substance and the metal. A method of mixing the raw materials is not particularly limited, and for example, a mortar or a stirring apparatus may be used. In addition, there may be used one or more kinds of mixing methods such as: powder mixing involving mixing the organic substance and metal in powder forms; and solvent mixing involving mixing the organic substance and the metal with a solvent added thereto.

The carbonization of the raw materials is performed by heating the raw materials and keeping the raw materials at a predetermined temperature at which the rawmaterials are carbonized (carbonization temperature). The carbonization temperature is not particularly limited as long as the rawmaterials are carbonized at the temperature, and for example, the carbonization temperature may be <NUM> or more. More specifically, the carbonization temperature may be, for example, <NUM> or more and <NUM>,<NUM> or less.

A rate of temperature increase in the heating of the raw materials to the carbonization temperature is not particularly limited, and for example, may be <NUM>/min or more and <NUM>/min or less. A period of time for which the raw materials are kept at the carbonization temperature is not particularly limited as long as the raw materials are carbonized in the period of time, and for example, the period of time may be <NUM> minutes or more, or may be <NUM> minutes or more and <NUM> minutes or less. In addition, the carbonization is preferably performed under an inert gas such as nitrogen (for example, under a stream of the inert gas).

The carbonized material formed by the carbonization of the raw materials as described above may be directly used as the support. In addition, the support may be formed of a pulverized carbonized material. A method of pulverizing the carbonized material is not particularly limited, and for example, there may be preferably used a pulverizing apparatus such as a ball mill or a bead mill. The average particle size of the carbonized material after the pulverization may be, for example, <NUM> or less.

The support may be formed of a carbonized material subjected to metal-removing treatment. The metal-removing treatment is treatment for removing a metal contained in the carbonized material and derived from the raw materials. The metal-removing treatment is not particularly limited as long as the treatment removes the metal contained in the carbonized material or decreases the amount of the metal, and for example, washing treatment with an acid or electrolytic treatment may be performed.

The acid to be used for the washing treatment with an acid is not particularly limited as long as an effect of the metal-removing treatment is obtained, and any one or more kinds of acids may be used. That is, for example, there may be used one or more kinds selected from a group consisting of hydrochloric acid (for example, dilute hydrochloric acid and concentrated hydrochloric acid), nitric acid (for example, dilute nitric acid and concentrated nitric acid), and sulfuric acid (for example, dilute sulfuric acid and concentrated sulfuric acid). A method for the washing treatment with an acid is not particularly limited, and for example, there may be preferably used a method involving immersing and keeping the carbonized material in a solution containing the acid.

The metal to be supported on the support is not particularly limited as long as the metal catalyzes a methanation reaction of carbon monoxide. Examples thereof may include one or more kinds selected from a group consisting of Ni, Ru, Rh, Pd, Pt, Ir, Cu, W, Cs, K, Na, Co, Fe, Ca, Mg, Ba, Sr, and Li.

When supporting Ni as a metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide, the support may have: a ratio of a peak area in the range of from more than <NUM> eV to <NUM> eV or less to a peak area in the range of from <NUM> eV or more to <NUM> eV or less, the peak areas being obtained by XPS measurement of the electron state of the 2p orbitals of the Ni, (hereinafter referred to as "XPS peak area ratio") of <NUM> or more; and a molar ratio of an H<NUM> desorption amount in the range of from <NUM> to <NUM>, which is obtained by an H<NUM> temperature-programmed desorption method, to a CO desorption amount in the range of from <NUM> to <NUM>, which is obtained by a CO temperature-programmed desorption method, (hereinafter referred to as "H<NUM>/CO ratio") of <NUM> or more.

In this case, for example, the XPS peak area ratio may be <NUM> or more, or may be <NUM> or more. The upper limit value of the XPS peak area ratio is not particularly limited, and for example, the XPS peak area ratio may be <NUM> or less, or may be less than <NUM>.

In addition, for example, the H<NUM>/CO ratio may be <NUM> or more, may be <NUM> or more, or may be <NUM> or more. The upper limit value of the H<NUM>/CO ratio is not particularly limited, and for example, the H<NUM>/CO ratio may be <NUM> or less.

Efficient methanation of carbon monoxide is achieved by using, as the support for supporting a metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide as described above, the carbonized material obtained by carbonizing the raw materials containing the organic substance and the metal described above.

That is, in general, when a methanation reaction of carbon monoxide is performed using a metal-supported catalyst obtained by supporting a metal on a support, methane formed is decomposed over the reaction time, resulting in the deposition of carbon on the surface of the metal. Consequently, the catalytic activity of the metal is decreased or lost in some cases. In this regard, the use of the carbonizedmaterial as the support for the metal effectively suppresses the deposition of carbon on the surface of the metal due to the decomposition of methane.

Further, the inventors of the present invention have made extensive studies on the improvement of the activity of a catalyst for methanation. As a result, the inventors themselves have found that the carbonized material constituting the support effectively improves the methanation catalytic activity of a metal supported on the carbonized material.

That is, for example, when the support exhibits the XPS peak area ratio and H<NUM>/CO ratio described above, the methanation catalytic activity of the metal supported on the support is particularly effectively enhanced.

A metal-supported catalyst disclosed herein is a catalyst including: a support formed of a carbonized material obtained by carbonizing raw materials containing an organic substance and a metal (that is, the support described above); and a metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide, the metal being supported on the support.

In the catalyst disclosed herein, the metal to be supported on the support is not particularly limited as long as the metal catalyzes a methanation reaction of carbon monoxide. Examples thereof may include one or more kinds selected from a group consisting of Ni, Ru, Rh, Pd, Pt, Ir, Cu, W, Cs, K, Na, Co, Fe, Ca, Mg, Ba, Sr, and Li.

A method of supporting the metal on the support is not particularly limited, and for example, there may be used an impregnation method, an ion exchange method, a co-precipitation method, an electroplating method, or a vapor deposition method. Of those, an impregnation method may be preferably used. In the impregnation method, for example, the metal is supported on the support by impregnating the support in an aqueous solution containing the metal to be supported, and then removing the solvent of the aqueous solution. In addition, the metal supported on the support is preferably reduced before the use of the catalyst.

It should be noted that in the catalyst, the metal supported on the support is mainly supported on the surface of the carbonized material constituting the support. On the other hand, the metal to be used for the production of the carbonized material is dispersed in the raw materials. Therefore, in the catalyst, the metal derived from the raw materials for the carbonized material, and the metal supported on the carbonized material, exhibit different distributions.

When Ni is supported as the metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide, the catalyst may have: a ratio of a peak area in the range of from more than <NUM> eV to <NUM> eV or less to a peak area in the range of from <NUM> eV or more to <NUM> eV or less, the peak areas being obtained by XPS measurement of the electron state of the 2p orbitals of the Ni, (XPS peak area ratio) of <NUM> or more; and a molar ratio of an H<NUM> desorption amount in the range of from40°C to <NUM>, which is obtained by an H<NUM> temperature-programmed desorption method, to a CO desorption amount in the range of from <NUM> to <NUM>, which is obtained by a CO temperature-programmed desorption method, (H<NUM>/CO ratio) of <NUM> or more.

When the catalyst exhibits the XPS peak area ratio and H<NUM>/CO ratio described above, the methanation catalytic activity of Ni supported on the support is effectively enhanced, and thus the catalyst exhibits a particularly excellent methanation catalytic activity.

A methanation reaction apparatus disclosed herein is an apparatus including the metal-supported catalyst described above, the apparatus being used for a methanation reaction of carbon monoxide.

The apparatus is not particularly limited as long as the apparatus includes the catalyst disposed so that the catalyst is brought into contact with a gas containing carbon monoxide. That is, for example, the apparatus may include: a base material on which the catalyst is fixed; and a housing which holds the base material therein so that the catalyst is brought into contact with the gas containing carbon monoxide. In this case, for example, ceramics particles or a honeycomb support may be used as the base material. In addition, the apparatus may be produced by fixing the catalyst to the base material, and causing the resultant to be held in a tubular or rectangular parallelepiped-shaped housing. The mode of the reaction in the apparatus is not particularly limited as long as the catalyst and the gas to be treated are appropriately brought into contact with each other, and for example, any of a fixed bed system or a fluidized bed system may be employed.

A method disclosed herein is, for example, a method involving performing a methanation reaction of carbon monoxide using the catalyst. That is, in this case, the methanation reaction of carbon monoxide is performed by bringing the catalyst and the gas containing carbon monoxide into contact with each other, to thereby decrease the concentration of carbon monoxide contained in the gas.

More specifically, the method may be, for example, a method involving treating a first gas containing carbon monoxide using the catalyst to produce a second gas whose concentration of carbon monoxide is decreased compared to that of the first gas. In this case, a concentration of carbon monoxide in the gas is effectively decreased compared to that before the treatment with the catalyst.

The gas to be treated with the catalyst is not particularly limited as long as the gas contains carbon monoxide, and for example, the gas may further contain hydrogen. That is, in the method, a first gas containing carbon monoxide and hydrogen may be treated using the catalyst to produce a hydrogen-containing second gas whose concentration of carbon monoxide is decreased compared to that of the first gas.

More specifically, in a case where a reformed gas is used as the first gas, a hydrogen-containing gas having effectively improved suitability as a fuel for a fuel cell is efficiently produced by bringing the reformed gas and the catalyst into contact with each other to effectively decrease the concentration of carbon monoxide in the reformed gas.

In addition, in the method, the methanation reaction apparatus including the catalyst may be used. That is, in this case, a first gas containing carbon monoxide is treated using the apparatus to produce a second gas whose concentration of carbon monoxide is decreased compared to that of the first gas.

More specifically, for example, the first gas is made to flow from the upstream end of the apparatus into the inside of the apparatus, and the first gas and the catalyst disposed in the inside of the apparatus are brought into contact with each other to perform a methanation reaction of carbon monoxide. Then, the second gas whose concentration of carbon monoxide is decreased compared to that of the first gas is made to flow out from the downstream end of the apparatus.

It should be noted that the flow of the gas into the upstream end of the apparatus and the flow of the gas out from the downstream end of the apparatus maybe performed, for example, via pipes connected to the upstream end and the downstreamend, respectively. In addition, for example, the downstream end of the apparatus may be connected to a fuel cell via the pipe so that the gas produced with the apparatus (for example, a hydrogen-containing gas whose concentration of carbon monoxide is decreased compared to that before the treatment) is supplied to the fuel cell through the pipe.

In addition, the apparatus to be used in the method is not particularly limited as long as the apparatus includes the catalyst disposed so that the catalyst is brought into contact with the gas containing carbon monoxide as described above. That is, for example, the apparatus may include: a base material on which the catalyst is fixed; and a housing which holds the base material therein so that the catalyst is brought into contact with the gas containing carbon monoxide. In this case, for example, ceramics particles or a honeycomb support may be used as the base material. In addition, the apparatus may be produced by fixing the catalyst to the base material, and causing the resultant to be held in a tubular or rectangular parallelepiped-shaped housing. The mode of the reaction in the apparatus is not particularly limited as long as the catalyst and the gas to be treated are appropriately brought into contact with each other, and for example, any of a fixed bed system or a fluidized bed system may be employed.

In addition, the method is, for example, a method of selecting, from a plurality of candidate supports, a support for supporting a metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide, the method including: determining, for each of the plurality of candidate supports in a state of supporting Ni, whether or not a ratio of a peak area in the range of from more than <NUM> eV to <NUM> eV or less to a peak area in the range of from <NUM> eV or more to <NUM> eV or less, the peak areas being obtained by XPS measurement of the electron state of the 2p orbitals of the Ni, (XPS peak area ratio) is equal to or higher than a threshold set in advance of <NUM> or more; determining, for each of the plurality of candidate supports in a state of supporting Ni, whether or not a molar ratio of an H<NUM> desorption amount in the range of from <NUM> to <NUM>, which is obtained by an H<NUM> temperature-programmed desorption method, to a CO desorption amount in the range of from <NUM> to <NUM>, which is obtained by a CO temperature-programmed desorption method, (H<NUM>/CO ratio) is equal to or higher than a threshold set in advance of <NUM> or more; and selecting, from the plurality of candidate supports, a support for which it is determined that the ratio of the peak areas is equal to or higher than the threshold, and the molar ratio is equal to or higher than the threshold. That is, in this case, the method can be said to be a screening method for a support for supporting a metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide.

The candidate supports are not particularly limited as long as the candidate supports are each capable of supporting a metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide, and supports that are each formed of a carbon material are used. That is, a plurality of kinds of carbon materials may be used as the plurality of candidate supports.

The carbon material is carbonized material obtained by carbonizing the raw materials containing the organic substance and the metal described above.

In the method, first, each of the plurality of candidate supports is caused to support Ni as a metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide. That is, a plurality of Ni-supported catalysts including different candidate supports supporting Ni are produced.

Next, each of the Ni-supported catalysts is subjected to XPS measurement, and it is determined on the basis of the obtained results whether or not the XPS peak area ratio is equal to or higher than a threshold set in advance of <NUM> or more. The threshold for the XPS peak area ratio is not particularly limited as long as the threshold is <NUM> or more, and for example, the threshold may be <NUM> or more, or may be <NUM> or more. In addition, the upper limit value of the threshold for the XPS peak area ratio is not particularly limited, and for example, the threshold may be <NUM> or less, or may be less than <NUM>.

In addition, a CO temperature-programmed desorption method and an H<NUM> temperature-programmed desorption method are each carried out for each of the Ni-supported catalysts, and it is determined on the basis of the obtained results whether or not the H<NUM>/CO ratio is equal to or higher than a threshold set in advance of <NUM> or more. The threshold for the H<NUM>/CO area ratio is not particularly limited as long as the threshold is <NUM> or more, and for example, the threshold may be <NUM> or more, may be <NUM> or more, or may be <NUM> or more. In addition, the upper limit value of the threshold for the H<NUM>/CO area ratio is not particularly limited, and for example, the threshold may be <NUM> or less.

In the method, from the plurality of candidate supports, a candidate support having such characteristics that the XPS peak area ratio is equal to or higher than the threshold, and the H<NUM>/CO ratio is equal to or higher than the threshold, is selected as a preferred support for supporting a metal that exhibits a catalytic activity for a methanation reaction of carbon monoxide. Therefore, according to the method, a support that effectively enhances the methanation catalytic activity of a metal supported thereon is efficiently selected from the plurality of candidate supports.

Next, specific examples according to those embodiments are described.

First, raw materials to be carbonized were prepared. That is, a phenol resin (for spinning, manufactured by Gunei Chemical Industry Co. ) and cobalt phthalocyanine (purity: <NUM>%, manufactured by Tokyo Chemical Industry Co. ) were mixed in acetone so that the weight ratio of cobalt (Co) to the phenol resin was <NUM> wt%. The resultant mixture was subjected to ultrasonic stirring for <NUM> minutes, and the solvent was removed using an evaporator. After that, the mixture was dried under reduced pressure at <NUM> overnight to yield the raw materials.

Next, the raw materials prepared as described above were carbonized. That is, <NUM> of the raw materials was placed in a quartz boat, and the quartz boat was placed in the center of a quartz reaction tube (φ23. <NUM>×<NUM>). Then, the quartz reaction tube was purged with a high-purity nitrogen gas at a flow rate of <NUM>/min for <NUM> minutes.

After that, the quartz reaction tube was heated using an infrared image furnace (RHL410P, manufactured by Shinku Riko K. ) under a stream of a high-purity nitrogen gas (<NUM>/min), and its temperature was increased at a rate of temperature increase of <NUM>/min to <NUM>,<NUM>. Further, the quartz reaction tube was kept at <NUM>,<NUM> for <NUM> hour to carbonize the raw materials.

The carbonized material thus obtained by the carbonization of the raw materials was pulverized in a mortar. Further, <NUM> of the pulverized carbonized material and <NUM> pulverizing balls were put into a vessel, and pulverization treatment was performed using a planetary ball mill at a rotation speed of <NUM> rpm for <NUM> minutes. After that, the pulverized carbonized material was sieved with a sieve having an opening of <NUM>, and the carbonized material that had passed through the sieve was collected.

Next, the carbonized material, concentrated hydrochloric acid, and a stirring bar were put into a vial, followed by stirring using a magnetic stirrer for <NUM> hours, and then followed by suction filtration. This operation was repeated three times, and then the carbonized material was dried under reduced pressure at <NUM> overnight. Then, the carbonized material after the drying was obtained as a support for supporting a metal (NSC: nanoshell carbon).

Nickel (Ni) was supported on NSC produced as described above by an impregnation method involving using an aqueous solution of nickel nitrate (Ni(NO<NUM>)<NUM>·<NUM><NUM>O) (Special Grade reagent, manufactured by Wako Pure Chemical Industries, Ltd.

That is, the aqueous solution of nickel nitrate was weighed so that the weight ratio of Ni to NSC became <NUM> wt%. Next, the aqueous solution of nickel nitrate, NSC, and <NUM> of distilled water were charged into a recovery flask having a volume of <NUM>, followed by ultrasonic stirring for <NUM> minutes.

Further, the distilled water was evaporated from the mixture with a rotary evaporator (hot water bath temperature: <NUM>, rotation speed: <NUM> rpm), and the residue was dried under reduced pressure at <NUM> overnight. After that, the temperature was increased at a rate of temperature increase of <NUM>/min to <NUM> with a vertical image furnace (RHL-E25N, manufactured by Shinku Riko K. ) under a stream of a <NUM>% H<NUM> gas (Ar:H<NUM>=<NUM>:<NUM> (mL/min)), and kept at <NUM> for <NUM> hour, to thereby perform reduction. Thus, a metal-supported catalyst formed of NSC and Ni supported on the NSC (Ni/NSC) was obtained.

In addition, as a comparative example, carbon black (Vulcan XC-72R, manufactured by CABOT CORPORATION) (XC) was used in place of NSC as the support for supporting a metal, and a metal-supported catalyst in which Ni was supported on the XC (Ni/XC) was produced in the same manner as described above.

In addition, as another comparative example, lignite (LY) was used in place of NSC as the support for supporting a metal, and a metal-supported catalyst in which Ni was supported on the LY (Ni/LY) was produced by an ion exchange method involving utilizing a surface functional group present in the LY in a large amount.

It should be noted that the amount of Ni to be supported in Ni/XC and Ni/LY was adjusted so that the particle size of Ni supported in the Ni/XC and the particle size of Ni supported in the Ni/LY were about the same as the particle size of Ni supported in Ni/NSC. As a result, the weight ratio of Ni to XC in Ni/XC was determined to be <NUM> wt%, and the weight ratio of Ni to LY in Ni/LY was determined to be <NUM> wt%.

In order to observe the state of supported Ni and measure the Ni particle size, the metal-supported catalysts were each observed using a transmission electron microscope (JEM-<NUM>, manufactured by JEOL Ltd. That is, <NUM> of each metal-supported catalyst was put into a vial together with <NUM> of methanol, and subjected to ultrasonic stirring for <NUM> minutes to disperse the metal-supported catalyst in methanol. After that, <NUM>µL of the solution containing the metal-supported catalyst were placed on a microgrid made of copper, and the grid was put into the TEM, followed by observation at an accelerating voltage of <NUM> kV.

On the basis of the obtained TEM image, the particle size of Ni supported on the metal-supported catalyst was measured. That is, the diameters of <NUM> Ni particles in a TEM image at a magnification of <NUM> were measured, and their average value was calculated as the Ni particle size. In addition, a support for supporting a metal having no metal supported thereon (NSC) was similarly subjected to TEM observation.

In order to observe the state of supported Ni and measure the Ni crystallite size, the metal-supported catalysts were each subjectedto X-ray diffraction (XRD). That is, each metal-supported catalyst was uniformly dispersed and placed on a holder made of glass, and subjected to XRD measurement using an XRD apparatus (XRD-<NUM>, manufactured by SHIMADZU CORPORATION) under the conditions of CuKα, <NUM> kV, <NUM> mA, scanning range: <NUM> to <NUM>°, and scanning step: <NUM>°. The Ni crystallite size was calculated using an Ni(<NUM>) peak around <NUM>°.

<FIG> show the results of the TEM observation. <FIG> are TEM images of NSC, <FIG> are TEM images of Ni/NSC, <FIG> are TEM images of Ni/XC, and <FIG> are TEM images of Ni/LY.

As shown in <FIG>, NSC had a carbon structure (graphite-like structure) including a nanoshell structure specifically formed by carbonizing raw materials containing an organic substance and a metal. Specifically, as shown in <FIG>, the nanoshell structure was a graphite structure-like turbostratic structure that had been developed in the form of an onion-like laminate around Co fine particles contained in the raw materials. In addition, as shown in <FIG>, in Ni/NSC, Ni fine particles were supported on NSC, which had a carbon structure as described above, in a state of being dispersed.

In addition, as shown in <FIG>, <FIG>, in Ni/XC and Ni/LY, Ni fine particles were supported on XC and LY, which had clearly different carbon structures from that of NSC, in a state of being dispersed as in Ni/NSC.

<FIG> shows the results of evaluation of the Ni particle sizes and Ni crystallite sizes of the metal-supported catalysts. As shown in <FIG>, the three kinds of metal-supported catalysts had about the same Ni particle size and Ni crystallite size. That is, it was conceivable that, when a difference was found in characteristic among those three kinds of metal-supported catalysts, the difference was not due to differences in Ni particle size and Ni crystallite size, but due to another factor.

A methanation reaction of carbon monoxide using metal-supported catalyst was performed with a temperature-programmed desorption spectrometer (Multitask TPD, manufactured by BEL Japan, Inc. ) to evaluate the methanation catalytic activity of the metal-supported catalyst.

As the metal-supported catalyst, each of the following four kinds were used: Ni/NSC, Ni/XC, Ni/LY, and a metal-supported catalyst (Ni/Al<NUM>O<NUM>) obtained by supporting Ni on alumina (Al<NUM>O<NUM>). The Ni/Al<NUM>O<NUM> was produced using alumina in place of NSC as the support for supporting a metal by supporting Ni on alumina in the same manner as in the case of Ni/NSC. The weight ratio of Ni to alumina in Ni/Al<NUM>O<NUM> was <NUM> wt%.

First, <NUM> of the metal-supported catalyst were loaded into a reaction tube, and the inside of the system was evacuated using a turbomolecular pump (manufactured by Mitsubishi Heavy Industries, Ltd. Next, under a stream of an H<NUM> gas (<NUM>/min), the reaction tube was heated to increase its temperature at a rate of temperature increase of <NUM>/min to <NUM>, and the reaction tube was kept at <NUM> for <NUM> minutes, to thereby perform prereduction. After that, the inside of the system was purged with an He gas (<NUM>/min) for <NUM> minutes, to thereby discharge the H<NUM> gas remaining in the system and to decrease the temperature of the reaction tube to <NUM>.

Further, while a mixed gas containing carbon monoxide ((H<NUM>+CO)/He) (H<NUM>: <NUM>/min, CO: <NUM>/min, He: <NUM>/min) was made to flow through the system, the temperature of the reaction tube was increased at a rate of temperature increase of <NUM>/min to <NUM>, and the amount of methane (CH<NUM>) formed during the increase was measured with a quadrupole mass spectrometer (manufactured by CANON ANELVA CORPORATION).

<FIG> shows the results of evaluation of the methanation catalytic activities of the metal-supported catalysts. In <FIG>, the horizontal axis represents temperature (°C), the vertical axis represents methane formation reaction rate per unit weight (<NUM>) of Ni supported on a metal-supported catalyst, and the square, the circle, the triangle, and the rhombus represent the results of Ni/NSC, Ni/XC, Ni/LY, and Ni/Al<NUM>O<NUM>, respectively.

As shown in <FIG>, in the cases of using Ni/XC and Ni/LY, methane was formed at about <NUM> or more. On the other hand, in the case of using Ni/NSC, methane was formed at about <NUM> or more.

That is, the temperature at which the methanation reaction started was lower in the case of using Ni/NSC than in the cases of using Ni/XC and Ni/LY. In other words, it was demonstrated that Ni/NSC was capable of allowing the methanation reaction to start at a lower temperature than Ni/XC and Ni/LY.

On the other hand, the methanation reaction started at a lower temperature (about <NUM>) in the case of using Ni/Al<NUM>O<NUM> than in the case of using Ni/NSC. However, at temperatures of <NUM> or more, the methane formation rate in the case of using Ni/Al<NUM>O<NUM> was markedly lower than that in the case of using Ni/NSC.

Thus, it was confirmed that the use of Ni/NSC as the catalyst for methanation of carbon monoxide enabled effective removal of carbon monoxide contained in a hydrogen-containing gas and efficient production of a hydrogen-containing gas whose concentration of carbon monoxide was effectively decreased.

In order to grasp the electron state of Ni supported on a metal-supported catalyst, X-ray photoelectron spectroscopy (XPS) was performed for each of Ni/NSC, Ni/XC, and Ni/LY. That is, an XPS apparatus (AXIS NOVA, manufactured by SHIMADZU CORPORATION) was used, the metal-supported catalyst was placed on a carbon tape attached to an aluminum piece, and the whole was introduced into the apparatus. Then, XPS measurement was performed using AlKα as an X-ray source under the conditions of <NUM> kV and <NUM> mA.

<FIG> show the results of the XPS measurement of Ni/NSC, Ni/XC, and Ni/LY, respectively. As shown in <FIG>, it was confirmed that the shape of the 2p spectrum of Ni changed, that is, the electron state of the Ni changed, depending on the kind of support on which Ni was supported.

Specifically, for example, Ni/NSC and Ni/XC each showed a peak at <NUM> eV corresponding to metal Ni, and also showed peaks in a higher binding energy region. On the other hand, Ni/LY showed a main peak at <NUM> eV corresponding to metal Ni, and showed only small peaks in the higher binding energy region.

In view of the foregoing, in order to quantitatively confirm such a difference, the three kinds of metal-supported catalysts were compared to each other in terms of ratio of a peak area in the higher binding energy region to a peak area around <NUM> eV corresponding to metal Ni.

Specifically, the binding energy at which peaks underwent transition from the lower binding energy state (metal Ni) to the higher binding energy state was defined to be <NUM> eV, and the ratio of a peak area in the range of from more than <NUM> eV to <NUM> eV or less to a peak area in the range of from <NUM> eV or more to <NUM> eV or less (XPS peak area ratio described above) was determined.

The results were as follows: the XPS peak area ratio of Ni/LY was <NUM>, whereas the XPS peak area ratio of Ni/NSC was <NUM> and the XPS peak area ratio of Ni/XC was <NUM>. Therefore, the XPS peak area ratio of <NUM> or more was considered as one of the reasons that Ni/NSC exhibited an excellent methanation catalytic activity.

CO and H<NUM> temperature-programmed desorption methods (TPD) were carried out for each of Ni/NSC and Ni/XC using a temperature-programmed desorption spectrometer (Multitask TPD, manufactured by BEL Japan, Inc. It should be noted that an exact spectrum of Ni/LY was difficult to obtain because LY had a thermal decomposition temperature of about <NUM>.

<NUM> of the metal-supported catalyst were loaded into a reaction tube, and the inside of the system was evacuated using a turbomolecular pump (manufactured by Mitsubishi Heavy Industries, Ltd. Next, under a stream of an H<NUM> gas (<NUM>/min), the reaction tube was heated to increase its temperature at a rate of temperature increase of <NUM>/min from <NUM> to <NUM>, and the reaction tube was kept at <NUM> for <NUM> minutes, to thereby perform prereduction. After that, the inside of the system was purged with an He gas (<NUM>/min) for <NUM> minutes, to thereby discharge the H<NUM> gas remaining in the system and to decrease the temperature of the reaction tube to <NUM>.

Further, in this system, under a stream of a <NUM>% H<NUM> gas (H<NUM>:He=<NUM>:<NUM> (mL/min)) or a <NUM>% CO gas (CO:He=<NUM>:<NUM> (mL/min)), the reaction tube was kept at <NUM> for <NUM> minutes, to thereby adsorb H<NUM> or CO onto the metal-supported catalyst. After that, the inside of the system was purged with a He gas (<NUM>/min) for <NUM> minutes, to thereby discharge the H<NUM> gas or CO gas remaining in the system.

Further, the reaction tube was heated, and H<NUM> or CO that was desorbed during the period when the temperature of the reaction tube increased at a rate of temperature increase of <NUM>/min from <NUM> to <NUM> was confirmed with a quadrupole mass spectrometer (manufactured by CANON ANELVA CORPORATION).

On the basis of the results obtained as described above, the desorption amount of H<NUM> and desorption amount of CO from each metal-supported catalyst were each determined. That is, a calibration curve showing a correlation between the peak area of H<NUM> or CO and the H<NUM> or CO desorption amount was created by an H<NUM> temperature-programmed desorption method or CO temperature-programmed desorption method using a standard substance (MgH<NUM> or CaC<NUM>O<NUM>·H<NUM>O) for which the H<NUM> or CO desorption amount was able to be theoretically determined.

Specifically, with regard to H<NUM>, the H<NUM> temperature-programmed desorption method was carried out using a plurality of standard samples containing MgH<NUM> at different ratios (samples prepared by mixing MgH<NUM> and alumina (Al<NUM>O<NUM>) at different ratios, more specifically, samples from each of which <NUM>µmol or <NUM>,<NUM>µmol of H<NUM> were to be theoretically desorbed per <NUM> of the sample), and a correlation between the peak area of H<NUM> obtained by thermally decomposing the MgH<NUM> and the theoretical H<NUM> desorption amounts from the standard samples was determined.

In addition, with regard to CO, the CO temperature-programmed desorption method was carried out using a plurality of standard samples containing CaC<NUM>O<NUM>·H<NUM>O at different ratios (samples prepared by mixing CaC<NUM>O<NUM>·H<NUM>O and alumina (Al<NUM>O<NUM>) at different ratios, more specifically, samples from each of which <NUM>µmol or <NUM>µmol of CO were to be theoretically desorbed per <NUM> of the sample), and a correlation between the peak area of CO obtained by thermally decomposing the CaC<NUM>O<NUM>·H<NUM>O and the theoretical CO desorption amounts from the standard samples was determined.

Then, on the basis of the thus obtained calibration curves, and the peak area of H<NUM> and peak area of CO of each metal-supported catalyst described above obtained by the H<NUM> temperature-programmed desorption method and the CO temperature-programmed desorption method, the H<NUM> desorption amount and CO desorption amount from the metal-supported catalyst were respectively determined.

It should be noted that the supports of the metal-supported catalysts were carbon materials, and hence the CO desorption amount of each of the metal-supported catalysts was determined as a value obtained by subtracting the CO desorption amount measured for the support (NSC and XC) by the CO temperature-programmed desorption method from the CO desorption amount measured for the metal-supported catalyst (Ni/NSC and Ni/XC) by the CO temperature-programmed desorption method.

Further, the molar ratio of the H<NUM> desorption amount in the range of from <NUM> to <NUM>, which was obtained by the H<NUM> temperature-programmed desorption method, to the CO desorption amount in the range of from <NUM> to <NUM>, which was obtained by the CO temperature-programmed desorption method, (the H<NUM>/CO ratio described above) was calculated.

<FIG> show the results of the H<NUM> temperature-programmed desorption method and the CO temperature-programmed desorption method, respectively. In <FIG>, the horizontal axis represents temperature (°C), ) the vertical axis represents H<NUM> or CO desorption amount per unit weight (<NUM>) of Ni supported on the metal-supported catalyst (nA/g-Ni), the solid line represents the result of Ni/NSC, and the broken line represents the result of Ni/XC.

<FIG> shows the H<NUM> desorption amount and CO desorption amount (mmol/g-Ni) per unit weight (<NUM>) of Ni supported on each of the metal-supported catalysts, calculated from results of the H<NUM> temperature-programmed desorption method and the CO temperature-programmed desorption method, and H<NUM>/CO ratio calculated from the desorption amounts.

As shown in <FIG>, each of the H<NUM> desorption amount and CO desorption amount of Ni/NSC was markedly large compared to that of Ni/XC. That is, each of the H<NUM> adsorption amount and CO adsorption amount of Ni/NSC was confirmed to be markedly large compared to that of Ni/XC. In particular, the H<NUM> desorption amount of Ni/NSC was about <NUM> times as large as that of Ni/XC. That is, Ni/NSC was confirmed to be particularly excellent in H<NUM> adsorption.

In addition, as shown in <FIG>, the H<NUM>/CO ratio of Ni/XC was <NUM>, whereas that of Ni/NSC was <NUM>. That is, the H<NUM>/CO ratio of Ni/NSC was markedly high compared to that of Ni/XC.

In this context, in the methanation reaction in which CO is hydrogenated to form CH<NUM>, it is considered that the amount of H<NUM> held on the surface of the metal-supported catalyst is preferably large. That is, it is important in the hydrogenation of CO to suppress the deposition of carbon on the surface of the catalyst (Boudoard reaction).

Accordingly, for example, it is desired that CH<NUM> be formed through an attack by hydrogen before CO adsorbed on the surface of the catalyst forms surface carbide structures and the surface carbide structures are further bound to each other two-dimensionally to form deposited carbon. In addition, it is considered that hydrogen accumulated in the metal-supported catalyst can be effectively utilized as the hydrogen.

Claim 1:
Use of a support for supporting a first metal that exhibits a catalytic activity for methanation reaction of carbon monoxide, the support being formed of a carbonized material obtained by carbonizing raw materials being a mixture of an organic substance and Co as a second metal,
wherein the support, when supporting Ni as the first metal, has:
a ratio of a peak area in a range of from more than <NUM> eV to <NUM> eV or less to a peak area in a range of from <NUM> eV or more to <NUM> eV or less of <NUM> or more, the peak areas being obtained by XPS measurement of an electron state of 2p orbitals of the Ni; and
a molar ratio of an H<NUM> desorption amount in a range of from <NUM> to <NUM>, which is obtained by an H<NUM> temperature-programmed desorption method after adsorbing H<NUM> onto the support under a stream of a <NUM> % H<NUM> gas with H<NUM>:He = <NUM>:<NUM>/min at <NUM> for <NUM> minutes, to a CO desorption amount in a range of from <NUM> to <NUM>, which is obtained by a CO temperature-programmed desorption method after adsorbing CO onto the support under a stream of a <NUM> % CO gas with CO:He = <NUM>:<NUM>/min at <NUM> for <NUM> minutes, of <NUM> or more.