Chemistry of inorganic compounds – Hydrogen or compound thereof – Elemental hydrogen
Reexamination Certificate
2000-07-18
2003-06-10
Silverman, Stanley S. (Department: 1754)
Chemistry of inorganic compounds
Hydrogen or compound thereof
Elemental hydrogen
C423S650000, C423S648100, C502S342000, C502S343000, C502S346000, C252S373000
Reexamination Certificate
active
06576217
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-227588, filed Aug. 11, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a methanol reforming catalyst, a method of manufacturing a methanol reforming catalyst and a method of reforming methanol.
In recent years, the earth environmental problem attracts attentions. In this connection, a fuel cell attracts attentions as a means for efficiently producing an electric energy without giving rise to an air pollution problem and a water contamination problem. Particularly, since harmful gases such as nitrogen oxides and carbon monoxide are contained in a large amount in the waste gas discharged from the internal combustion engines of a motor car or the like, various measures have been taken to overcome the problem of the harmful gases. As one of the measures against the problem, vigorous researches are being made in an attempt to develop a motor car utilizing a polymer electrolyte fuel cell (PEFC) in place of the internal combustion engine.
In the polymer electrolyte fuel cell (PEFC), hydrogen (H
2
) is diffused within a polymer film as protons, and an electric energy is obtained from the electron migration accompanying the diffusion of the protons. In order to mount the polymer electrolyte fuel cell to a motor car, it is necessary to develop an efficient hydrogen manufacturing apparatus. Methanol is a cheap liquid fuel that can be easily synthesized from a fossil fuel. Also, methanol can be converted relatively easily into hydrogen by a catalytic reaction.
A steam reforming reaction represented by formula (1) given below is known to the art as a method of manufacturing hydrogen from methanol:
CH
3
OH+H
2
O→3H
2
+CO
2
−11.8 kcal/mol (1)
However, reaction (1) given above is an endothermic reaction, making it necessary to supply a large amount of heat from outside in order to maintain a predetermined temperature at which the catalyst performs its function. As a result, a large space is required in the case where a methanol reformer is mounted as a movable power source to, for example, a motor car, making it impractical to employ the steam reforming reaction (1) described above. Such being the situation, proposed are methods of manufacturing hydrogen by utilizing an exothermic reaction (2) or (3) given below, which involves an oxygen addition:
CH
3
OH+1/2O
2
→CO+H
2
+H
2
O+36.2 kcal/mol (2)
CH
3
OH+1/2O
2
→CO
2
+2H
2
+46.0 kcal/mol (3)
Among these exothermic reactions (2) and (3), reaction (3) is desirable. Specifically, exothermic reaction (3) permits manufacturing a larger amount of hydrogen gas (H
2
) used as a fuel of PEFC. In addition, CO that is a poisoning material to PEFC is not generated in the exothermic reaction (3).
It is conceivable to provide a hydrogen manufacturing apparatus, in which the heat amount balance is controlled, and which is compact and excellent in its start up performance, by allowing reactions (1) and (3) given above to proceed simultaneously. However, a catalyst of a high reactivity, which permits reactions (1) and (3) to proceed simultaneously, has not yet been developed. It is of high importance in this technical field to develop such a catalyst.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a methanol reforming catalyst, which promotes both the steam reforming reaction given by formula (1) and the partial oxidation reaction given by formula (3) simultaneously so as to achieve a high methanol conversion rate and suppress the carbon monoxide formation, and a method of manufacturing the particular methanol reforming catalyst.
Another object of the present invention is to provide a methanol reforming method, which promotes both the steam reforming reaction given by formula (1) and the partial oxidation reaction given by formula (3) simultaneously so as to achieve a high methanol conversion rate and suppress the carbon monoxide formation.
According to a first aspect of the present invention, there is provided a methanol reforming catalyst comprising an oxide containing Cu, Zn and Al.
According to a second aspect of the present invention, there is provided a method of manufacturing a methanol reforming catalyst, comprising the steps of allowing an aqueous solution containing a copper component, an aqueous solution containing a zinc component and an aqueous solution containing an aluminum component to react with a precipitant consisting of an alkaline aqueous solution to bring about precipitation under an alkaline conditions so as to obtain a basic metal carbonate containing Cu, Zn and Al as a precipitate, washing the precipitate of the basic metal carbonate, and sintering the precipitate.
In the method of the present invention for manufacturing the methanol reforming catalyst, it is possible to add the three kinds of the aqueous solutions simultaneously or separately for the reaction with the precipitant.
According to a third aspect of the present invention, there is provided a method of manufacturing a methanol reforming catalyst, comprising the steps of allowing an aqueous solution containing a copper component, an aqueous solution containing a zinc component, an aqueous solution containing an aluminum component, and an aqueous solution containing metal component consisting of at least one element selected from the group consisting of La, Ca, Ga, Zr, Ce, Cr, Ba and Mg to react with a precipitant consisting of an alkaline aqueous solution to bring about precipitation under an alkaline conditions so as to obtain a basic metal carbonate containing Cu, Zn, Al and at least one element selected from the group consisting of La, Ca, Ga, Zr, Ce, Cr, Ba and Mg as a precipitate, washing the precipitate of the basic metal carbonate, and sintering the precipitate.
In the method of the present invention for manufacturing the methanol reforming catalyst, it is possible to add the four kinds of the aqueous solutions simultaneously or separately for the reaction with the precipitant.
According to a fourth aspect of the present invention, there is provided a methanol reforming method, comprising the step of bringing a gas containing methanol, steam and oxygen into contact with a methanol reforming catalyst having an oxide containing Cu, Zn and Al so as to allow methanol to react with the steam and oxygen, thereby forming a hydrogen-containing gas.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
DETAILED DESCRIPTION OF THE INVENTION
A methanol reforming catalyst of the present invention will now be described.
The methanol reforming catalyst of the present invention contains a complex oxide having Cu, Zn and Al as metal components. In the present invention, an evaporated methanol is allowed to react with steam and oxygen in the presence of the methanol reforming catalyst so as to form a hydrogen-containing gas.
“The complex oxide” is not a mixture of plural metal oxides, but is a compound containing Cu, Zn and Al.
It is desirable for the oxide to further contain at least one element selected from the group consisting of La, Ca, Ga, Zr, Ce, Cr, Ba and Mg in addition to Cu, Zn and Al noted above.
The complex oxide should desirably have a composition represented by general formula (1) given below:
(CuO)
w
(ZnO)
x
(Al
2
O
3
)
y
M
z
(1)
where M is at least one kind of an oxide selected from the group consisting of lanthanum oxide, calcium oxide, gallium oxide, zirconium oxide, cerium oxide, chromium oxide, barium oxide and magnesium oxide, and the molar ratios w, x, y and z should be: w=
Nojima Shigeru
Yasutake Toshinobu
Lish Peter J
Mitsubishi Heavy Industries Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Silverman Stanley S.
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