Chemistry of inorganic compounds – Hydrogen or compound thereof – Elemental hydrogen
Reexamination Certificate
2001-10-25
2003-11-04
Langel, Wayne A. (Department: 1754)
Chemistry of inorganic compounds
Hydrogen or compound thereof
Elemental hydrogen
C423S437200, C423S651000, C423S652000, C423S655000, C423S656000
Reexamination Certificate
active
06641795
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a reformer for hydrogen generation, suitably used in industries and vehicles; a catalytic reactor; an electrically heatable catalyst used in said reformer or catalytic reactor; and a method for operation of said reformer.
(2) Description of the Related Art
In recent years, production of electricity without causing environmental pollution has drawn attention and an interest in fuel cell has increased. Fuel cell has various advantages such as high efficiency in power generation, formation of small amount of carbon dioxide (CO
2
) and substantially no formation of harmful substances such as carbon monoxide (CO), nitrogen oxides (NOx) and the like. Therefore, researches and developments on use of fuel cell in on-site type power generator or automobile have been under way recently. In generating electricity using a fuel cell, high-purity hydrogen is required. This hydrogen is produced by using, as a starting material, a hydrocarbon (e.g. butane or propane), an alcohol (e.g. methanol), CO or the like and conducting a catalytic reaction.
The main reaction in the above hydrogen production is steam reforming which takes place in the presence of steam and a catalyst. Since the steam reforming is generally an endothermic reaction although it differs depending upon the starting material used, it is important to heat the catalyst to a desired temperature uniformly. Decrease in reaction temperature invites formation of coke and resultant deactivation of catalyst; therefore, great care is necessary in industrial designing of the reactor.
Further, since the above steam reforming has a low reaction speed unlike combustion reaction, a relatively large catalyst volume is required in treating a given amount of a starting material. Meanwhile, the catalyst functions at high temperatures. Hence, a long time is taken to warm up the catalyst. Thus, there have been problems when the steam reforming is utilized in an on-site generator or an automobile where quick hydrogen generation is required.
In conventional catalytic processes for hydrogen production by steam reforming, the catalyst used has generally been heated externally. When a starting material is passed over a fixed catalyst bed and a relatively large reaction tube is used, it is difficult to transfer a heat to the center of the catalyst bed and there has been used a complicated mechanism that a tubular reactor is heated by the use of a heating medium such as metal bath, combustion waste gas or the like.
In other conventional catalytic process for hydrogen production by steam reforming, the heating of the catalyst used has been conducted by introducing a combustion waste gas (generated in gas-phase reaction or catalytic combustion) into the reaction tube and heating the catalyst with the heat of the waste gas. This process is not preferred because it increases the flow amount of fluid, reducing the activity of intended reaction and generating more CO
2
by combustion.
In the gas produced by the steam reforming, hydrogen has no sufficient purity to be used in a fuel cell and CO has a deactivating effect on the Pt-based electrode used in the fuel cell. Therefore, a CO shift reaction (an aqueous conversion reaction) and a CO selective oxidation reaction are conducted to increase the purity of hydrogen. However, there are many technical problems as to the way in which the catalysts used therein are heated so as to function or the way in which the reactions are allowed to proceed stably.
As other process for generating hydrogen from a hydrocarbon or the like, there is a process which comprises generating hydrogen and CO by a partial oxidation reaction of a hydrocarbon in place of the above-mentioned steam reforming and then conducting the above-mentioned CO shift reaction and CO selective oxidation reaction to obtain hydrogen. In this process, the partial oxidation reaction of the first step is an exothermic reaction and is substantially free from the problem of heat supply; however, since the reaction temperature is generally higher than that of the steam reforming, technical problems remain unsolved as to how the catalyst temperature is maintained and how high-purity hydrogen is generated in a short time when the process is utilized in an on-site generator or an automobile. Also as other process for generating hydrogen from a hydrocarbon or the like, there is a process using a decomposition reaction. A specific example of the decomposition reaction is a decomposition reaction for generating hydrogen from methanol. This reaction is an endothermic reaction similarly to the steam reforming, and there are the same problems as mentioned above.
Also in industries where hydrogen is consumed in a large amount, such as ammonia synthesis, hydrogenation, hydrodesulfurization and the like, there are many technical problems to be solved in areas such as reaction efficiency, operational energy, period of reactor start-up and conversion of starting material.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems of the prior art, the present invention aims at providing a reformer capable of generating high-purity hydrogen for fuel cell used in industries or automobile, in a short time; a catalytic reactor; an electrically heatable catalyst unit used therein; and a method for operation of the reformer.
According to the present invention, there is provided, as a first invention,
a reformer disposed in the flow path of a reactant fluid, which comprises:
a catalyst unit capable of generating hydrogen from a reactant fluid containing an organic compound or carbon monoxide, by catalysis, and
an electrically heatable heater unit.
According to the present invention, there is also provided, as a second invention,
a reformer disposed in the flow path of a reactant fluid, which comprises a catalyst unit capable of generating hydrogen from a reactant fluid containing an organic compound or carbon monoxide, by catalysis, wherein at least part of the catalyst unit is constituted so as to be electrically heatable.
According to the present invention, there is also provided, as a third invention,
an electrically heatable catalyst unit comprising:
any of a sintered material, a metallic material, a composite material thereof, at least a portion of each of these materials having an electrically heatable property, and a composite material of (1) a heat-resistant material having no electrically heatable property and (2) said sintered material and/or said metallic material, and
a catalyst capable of generating hydrogen from a reactant fluid containing an organic compound or carbon monoxide, by catalysis,
which catalyst unit has porosity, thereby enables diffusion of a reactant fluid therethrough, and is electrically heatable.
According to the present invention, there are also provided, as a fourth invention and a fifth invention,
a method for operation of a reformer disposed in the flow path of a reactant fluid and comprising a catalyst unit capable of generating hydrogen from a reactant fluid containing an organic compound or carbon monoxide, by catalysis, and an electrically heatable heater unit, which method comprises electrically heating the heater unit at the start-up of the reformer and thereby generating hydrogen, and
a method for operation of a reformer disposed in the flow path of a reactant fluid and comprising a catalyst unit capable of generating hydrogen from a reactant fluid containing an organic compound or carbon monoxide, by catalysis, at least part of the catalyst unit being constituted so as to be electrically heatable, which method comprises electrically heating the catalyst unit at the start-up of the reformer and thereby generating hydrogen.
According to the present invention, there are also provided, as a sixth invention and a seventh invention,
a method for operation of a reformer disposed in the flow path of a reactant fluid and comprising a catalyst unit capable of generating hydrogen from a reactant fluid containing an organic compound or carbon monoxide, by c
Langel Wayne A.
NGK Insulators Ltd.
Parkhurst & Wendel L.L.P.
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