Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Carbon monoxide component
Reexamination Certificate
2000-06-07
2002-11-19
Langel, Wayne A. (Department: 1754)
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Carbon monoxide component
C252S373000, C423S437200, C423S648100
Reexamination Certificate
active
06482378
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-160613, filed Jun. 8, 1999; and No. 2000-024199, filed Feb. 1, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a catalyst for selective oxidation of carbon monoxide, a selective removing method of carbon monoxide, a hydrogen refining catalyst for selectively oxidizing CO and CH
3
OH of a gaseous mixture containing H
2
, CH
3
OH, CO and O
2
and a hydrogen refining method for removing CO and CH
3
OH from a gaseous mixture containing H
2
, CH
3
OH and CO.
A polymer electrolyte fuel cell permits suppressing generation of a pollutant causing an air pollution, is high in its heat efficiency and, thus, is expected to be used widely as a low temperature operation type fuel cell in a motor car power source, a dispersed power source or the like. A platinum catalyst is used mainly in the electrode of the polymer electrolyte fuel cell. Since the platinum catalyst tends to be poisoned by carbon monoxide (CO), it is necessary remove CO from the fuel gas as much as possible. The fuel gas is manufactured by, for example, reforming the fuel such as methanol by means of steam reforming reaction or a partial oxidation reaction so as to produce a hydrogen gas. Then, CO formed as a by-product in the hydrogen manufacturing reaction is removed by a CO shift reaction of CO+H
2
O CO
2
+H
2
.
The removal of CO by the CO shift reaction is limited under the restriction in terms of the chemical equilibrium. For example, where a hydrogen gas is manufactured from methanol, followed by applying the CO shift reaction to the hydrogen-containing reaction mixture, the resultant gaseous composition contains about 40 to 60% of H
2
, about 10% of CO
2
, about 20% of H
2
O, and about 0.5% of CO. It should be noted that, in order to prevent the polymer electrolyte fuel cell from being poisoned by CO, it is necessary to lower the CO concentration to 100 ppm or lower. Such being the situation, it is necessary to take measures for further lowering the CO concentration in combination with the CO shift reaction.
As a measure for removing CO contained in the hydrogen-based raw material gas, studied is a method in which an oxidizing agent of O
2
is added to the raw material gas and is brought into contact with the raw material gas so as to selectively oxidize CO contained in the raw material gas.
In the conventional catalyst, however, almost all the oxygen gas added to the raw material gas reacts with hydrogen, which is the main constituent of the raw material gas, so as to preferentially burn the hydrogen. As a result, CO is left unremoved from the raw material gas.
On the other hand, Japanese Patent Disclosure (Kokai) No. 6-296870 as claimed discloses a catalyst for cleaning the waste gas. It is taught that the catalyst consists of at least one metal selected from the platinum group elements, which is supported on a crystalline silicate having an X-ray diffraction pattern shown in Table A given in this prior art and represented in terms of the molar ratio of the oxide in a dehydrated state by a chemical formula (1±0.8)R
2
O.[aM
2
O
3
.bM′O.cAl
2
O
3
].ySiO
2
, where R denotes an alkali metal ion and/or hydrogen ion, M denotes an ion of at least one element selected from the group consisting of VIII group elements, rare earth elements, Ti, V, Cr, Nb, Sb and Ga, M′ denotes an ion of alkaline earth metals of Mg, Ca, Sr, Ba, 0<a, 0≦b<20, a+c=1, and 11<y<3000.
This prior art also teaches in columns [0008] to [0009] that the particular waste gas cleaning catalyst permits cleaning the waste gas containing NOx, CO and HC in accordance with reaction formulas (1) to (4) given below:
(1) C
3
H
6
+3/2O
2
→3CH
2
O
(2) CH
2
O+O
2
→CO
2
+H
2
O
(3) CH
2
O+2NO→N
2
+CO
2
+H
2
O
(4) CO+1/2O
2
→CO
2
Reaction (1) given above represents activation of HC, reaction (2) represents combustion of HC, reaction (3) represents a denitrification, and reaction (4) represents combustion of CO.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a catalyst for selectively oxidizing carbon monoxide, the catalyst being capable of selectively oxidizing CO contained in a gaseous mixture containing H
2
, CO and an oxidizing agent of O
2
.
Another object is to provide a selective carbon monoxide removing method that permits selectively removing CO from a gaseous mixture containing H
2
and CO.
Another object is to provide a hydrogen refining catalyst capable of selectively oxidizing CO and CH
3
OH contained in a gaseous mixture containing H
2
, CO, CH
3
OH and an oxidizing agent of O
2
with a high selective oxidizing capability.
Still another object is to provide a hydrogen refining method capable of selectively oxidizing and removing CO and CH
3
OH contained in a gaseous mixture containing H
2
, CO and CH
3
OH with a high removal rate.
According to a first aspect of the present invention, there is provided a selective carbon monoxide oxidizing catalyst capable of selectively oxidizing CO contained in a gaseous mixture containing H
2
, CO and an oxidizing agent of O
2
, comprising a carrier and an active metal consisting of at least one kind of metal selected from the group consisting of Pt, Pd, Ru, Rh and Ir and supported on the carrier, the carrier being a crystalline silicate having the highest to the fifth highest peaks in the powder X-ray diffraction using CuK&agr; ray in the lattice spacing of 3.65±0.1 Å, 3.75±0.1 Å, 3.85±0.1 Å, 10.0±0.3 Å, and 11.2±0.3 Å, and having the composition represented by formula (1) under a dehydrated state:
(1±0.8)R
2
O.[aM
2
O
3
.bNO.cAl
2
O
3
].ySiO
2
(1)
where R denotes at least one element selected from the group consisting of an alkali metal and H, M denotes at least one element selected from the group consisting of VIII group elements, rare earth elements, Ti, V, Cr, Nb, Sb and Ga, N denotes at least one element selected from the group consisting of Mg, Ca, Sr, and Ba, and the molar ratios a, b, c and y are: 0≦a, 0≦b≦20, a+c=1, and 11≦y≦3000.
According to a second aspect of the present invention, there is provided a selective removing method of carbon monoxide, comprising the step of bringing a gaseous mixture containing H
2
, CO and an oxidizing agent of O
2
into contact with a selective oxidizing catalyst of carbon monoxide for selectively oxidizing and removing CO from the gaseous mixture, the selective oxidizing catalyst of carbon monoxide comprising a carrier and an active metal consisting of at least one kind of metal selected from the group consisting of Pt, Pd, Ru, Rh and Ir and supported on the carrier, the carrier being a crystalline silicate having the highest to the fifth highest peaks in the powder X-ray diffraction using CuK&agr; ray in the lattice spacing of 3.65±0.1 Å, 3.75±0.1 Å, 3.85±0.1 Å, 10.0±0.3 Å, and 11.2±0.3 Å, and having the composition represented by formula (1) under a dehydrated state:
(1±0.8)R
2
O.[aM
2
O
3
.bNO.cAl
2
O
3
].ySiO
2
(1)
where R denotes at least one element selected from the group consisting of an alkali metal and H, M denotes at least one element selected from the group consisting of VIII group elements, rare earth elements, Ti, V, Cr, Nb, Sb and Ga, N denotes at least one element selected from the group consisting of Mg, Ca, Sr, and Ba, and the molar ratios a, b, c and y are: 0≦a, 0≦b≦20, a+c=1, and 11≦y≦3000.
According to a third aspect of the present invention, there is provided a selective removing method of carbon monoxide, comprising the steps of:
preparing a reactor loaded with a catalyst bed housing a selective carbon mono
Nojima Shigeru
Yasutake Toshinobu
Langel Wayne A.
Medina Maribel
Mitsubishi Heavy Industries
LandOfFree
Selective removing method of carbon monoxide and hydrogen... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Selective removing method of carbon monoxide and hydrogen..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Selective removing method of carbon monoxide and hydrogen... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2961206