Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
1999-03-11
2002-04-23
Griffin, Steven P. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C423S418200, C423S651000, C423S653000
Reexamination Certificate
active
06376423
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a catalyst for producing a synthesis gas and to a process for the production of carbon monoxide.
BACKGROUND ART
A synthesis gas is a mixed gas containing hydrogen and carbon monoxide and is widely used as a raw material for the synthesis of ammonia, methanol, acetic acid, etc.
Such a synthesis gas may be produced by reaction of a hydrocarbon with steam and/or carbon dioxide in the presence of a catalyst. In the reaction, however, carbon deposition reactions occur as side reactions to cause carbon deposition which brings about a problem of catalyst poisoning.
The raw materials for the carbon deposition are a carbon-containing organic compound used as a raw material and CO produced in situ. The carbon deposition is accelerated as the partial pressures of these raw materials increase. Therefore, it is possible to reduce the amount of the carbon deposition by increasing the feed amount of steam and carbon dioxide while reducing the reaction pressure. In this case, however, it is necessary to excessively use steam and carbon dioxide in order to reduce the partial pressures of the carbon-containing organic compound and CO, so that several disadvantages are caused. For example, consumption of heat energy required for preheating steam and carbon dioxide increases. Further, costs for the separation of these gases from the product increase. Moreover, since a large reaction apparatus is required, the apparatus costs increase.
JP-A-5-208801 discloses a carbon dioxide-reforming catalyst containing a Group VIII metal supported on high purity, super-fine single crystal magnesium oxide. JP-A-6-279003 discloses a carbon dioxide-reforming catalyst containing a ruthenium compound supported on a carrier composed of a compound of at least one alkaline earth metal oxide and aluminum oxide. JP-A-9-168740 discloses a carbon dioxide-reforming catalyst containing rhodium supported on a carrier formed of a Group II-IV metal oxide or a lanthanoid metal oxide or a composite carrier composed of the above metal oxide and alumina. The reaction experiments using these catalysts are performed under ambient pressure. At a high pressure, which is industrially significant, these catalysts show a high carbon deposition activity and, hence, are not satisfactory as industrially applicable catalysts.
Carbon monoxide is widely utilized as a raw material for the synthesis of industrial products by, for example, hydroformylation. Carbon monoxide is generally produced by the reforming of methane with steam according to the reaction shown below to obtain a synthesis gas, from which carbon monoxide is subsequently separated:
CH
4
+H
2
O
H
2
+CO.
In this reaction, however, only 1 mole of carbon monoxide is produced per 3 mole of hydrogen. Thus, the process for the production of carbon monoxide is not efficient. In contrast, the reforming of methane with carbon dioxide proceeds as follows:
CH
4
+CO
2
2H
2
+2CO.
Thus, hydrogen and carbon monoxide are produced in an equimolar amount so that this process is more efficient than the reforming with steam. In this case, when carbon dioxide is added in excess relative to methane, carbon monoxide is produced from carbon dioxide and hydrogen by the following reverse shifting reaction:
CO
2
+H
2
CO+H
2
O,
so that the concentration of carbon monoxide in the product gas further increases. Therefore, the reforming with carbon dioxide is effective in the production of carbon monoxide. However, the product gas obtained by this reaction has a composition in an equilibrium which favors the carbon deposition, so that the catalyst used for this reaction causes considerable deactivation of the catalyst.
The objects of the present invention are:
(1) to provide a catalyst for use in a process for the production of a synthesis gas by reaction of a carbon-containing organic compound with steam and/or carbon dioxide, which catalyst has suppressed carbon deposition activity;
(2) to provide a catalyst for use in a process for the production of a synthesis gas by reaction of a carbon-containing organic compound with oxygen, which catalyst has suppressed carbon deposition activity; and
(3) to provide a process which includes a step of reacting a carbon-containing organic compound with carbon dioxide to produce a synthesis gas, and a step of concentrating carbon monoxide in the thus obtained synthesis gas and which can produce carbon monoxide in an economically favorable manner by using a catalyst having suppressed carbon deposition activity in the synthesis gas producing step.
Other objects of the present invention will be understood from the following description of the specification.
DISCLOSURE OF THE INVENTION
The present inventors have made an intensive study to accomplish the above-described objects and, as a result, have completed the present invention.
In accordance with the present invention there is provided a catalyst for producing a synthesis gas comprising a carrier formed of a metal oxide and at least one catalytic metal selected from rhodium, ruthenium, iridium, palladium and platinum and supported on said carrier, characterized in that said catalyst has a specific surface area of 25 m
2
/g or less, in that the electronegativity of the metal ion of said carrier metal oxide is 13.0 or less and in that the amount of said supported catalytic metal is 0.0005-0.1 mole %, in terms of a metal, based on said carrier metal oxide.
The present invention also provides a process for producing carbon monoxide, which comprises a step of reacting a carbon-containing organic compound with carbon dioxide at an elevated temperature in a pressurized condition in the presence of a catalyst to produce a synthesis gas, and a step of concentrating carbon monoxide in the thus obtained synthesis gas, said process being characterized in that said catalyst comprises a carrier formed of a metal oxide and at least one catalytic metal selected from rhodium, ruthenium, iridium, palladium and platinum and supported on said carrier, in that said catalyst has a specific surface area of 25 m
2
/g or less, in that the electronegativity of the metal ion of said carrier metal oxide is 13.0 or less and in that the amount of said catalytic metal is 0.0005-0.1 mole %, in terms of metal, based on said carrier metal oxide.
The catalyst of the present invention is used for the production of a synthesis gas using a carbon-containing organic compound as a raw material. In this case, the processes for producing a synthesis gas include various conventionally known processes, for example, (i) a process in which a carbon-containing organic compound is reacted with steam, (ii) a process in which a carbon-containing organic compound is reacted with carbon dioxide, (iii) a process in which a carbon-containing organic compound is reacted with a mixture of steam with carbon dioxide and (iv) a process in which a carbon-containing organic compound is reacted with oxygen.
The catalyst of the present invention contains at least one catalytic metal selected from rhodium (Rh), ruthenium (Ru), iridium (Ir), palladium (Pd) and platinum (Pt) supported on a carrier metal oxide having specific characteristics. In this case, the catalytic metal can be supported in the form of a metallic state or in the form of a metal compound such as an oxide.
The catalyst of the present invention is characterized in that the catalyst has activity required for converting a carbon-containing organic compound into a synthesis gas while exhibiting a function to significantly suppress side reactions of carbon deposition reactions.
The catalyst according to the present invention can significantly suppress the carbon deposition reactions is characterized in that:
(i) the electronegativity of the metal ion of the carrier metal oxide is 13.0 or less;
(ii) the catalyst has a specific surface area of 25 m
2
/g or less; and
(iii) the amount of the supported catalytic metal is 0.0005-0.1 mole % based on the carrier metal oxide. Such a catalyst having a considerably suppressed carbon deposition activity
Asaoka Sachio
Nagumo Atsuro
Shimura Mitsunori
Wada Yukitaka
Wakamatsu Shuhei
Chiyoda Corporation
Griffin Steven P.
Lorusso & Loud
Strickland Jonas N.
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