Compositions – Gaseous compositions – Carbon-oxide and hydrogen containing
Reexamination Certificate
1999-03-11
2002-01-22
Griffin, Steven P. (Department: 1754)
Compositions
Gaseous compositions
Carbon-oxide and hydrogen containing
C423S418200, C423S650000, C423S652000, C502S326000
Reexamination Certificate
active
06340437
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for producing a synthesis gas by an autothermal reforming method.
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 carbon-containing organic compound with steam and/or carbon dioxide in the presence of a catalyst. Since the reaction resulting in the formation of such a synthesis gas is very highly exothermic, a large amount of energy is required in order to maintain a reaction temperature (600-1,000° C.). Such a large amount of energy can be obtained by partially oxidizing a carbon-containing organic compound.
A process for the production of a synthesis gas including partial oxidation of a carbon-containing organic compound is carried out by partially oxidizing the carbon-containing organic compound to obtain a high temperature mixed gas having a temperature of at least 600° C. and containing an unreacted carbon-containing organic compound. The unreacted carbon-containing organic compound contained in the mixed gas is reacted with carbon dioxide and/or steam in the presence of a catalyst. In this method, however, carbon deposition reactions occur as side reactions to cause carbon deposition, when the unreacted carbon-containing organic compound contained in the mixed gas is reacted with carbon dioxide and/or steam to form the synthesis gas. The deposited carbon causes a problem, because the catalyst is poisoned.
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.
The objects of the present invention are:
(1) to provide a process for the production of a synthesis gas which includes a step of partially oxidizing a carbon-containing organic compound and a step of reacting an unreacted carbon-containing organic compound contained in the thus obtained high temperature mixed gas with carbon dioxide and/or steam in a pressurized condition and which can solve a problem of carbon deposition.
(2) to provide a process in which a catalyst having suppressed carbon deposition activity is used for the reaction of the unreacted carbon-containing organic compound contained in the high temperature mixed gas with carbon dioxide and/or steam.
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 process for producing a synthesis gas from a carbon-containing organic compound, characterized
(i) in that said carbon-containing organic compound is partially oxidized to form a mixed gas having a temperature of at least 600° C. and containing an unreacted carbon-containing organic compound,
(ii) in that said unreacted carbon-containing organic compound contained in said high temperature mixed gas is reacted with carbon dioxide and/or steam under pressurized conditions in the presence of a catalyst, and
(iii) 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, said catalyst having a specific surface area of 25 m
2
/g or less, metal ion of said carrier metal oxide having electronegativity of 13.0 or less, the amount of said catalytic metal supported being 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 a synthesis gas from a carbon-containing organic compound, characterized
(i) in that a catalyst is fluidized by a blended gas containing said carbon-containing compound, air and/or oxygen, and carbon dioxide and/or steam,
(ii) said carbon-containing organic compound contained in said blended gas by which said catalyst is fluidized is partially oxidized to form a mixed gas having a temperature of at least 600° C. and containing an unreacted carbon-containing organic compound, said unreacted carbon-containing organic compound being reacted with carbon dioxide and/or steam under pressurized conditions, and
(iii) 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, said catalyst having a specific surface area of 25 m
2
/g or less, metal ion of said carrier metal oxide having electronegativity of 13.0 or less, the amount of said catalytic metal supported being 0.0005-0.1 mole %, in terms of a metal, based on said carrier metal oxide.
The catalyst used in the present (hereinafter referred to also as catalyst of the present invention) 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 used in 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 has been first found by the present inventors.
The metal oxide used as a carrier may be a single metal oxide or a mixed metal oxide. In the present invention, the electronegativity of the metal ion in the carrier metal oxide is 13 or less, preferably 12 or less, more preferably 10 or less. The lower limit is about 4. Thus, the electronegativity of the metal ion in the carrier metal oxide used in the present invention is 4-13, preferably 4-12. The electronegativity of the
Asaoka Sachio
Nagumo Atsuro
Shimura Mitsunori
Wada Yukitaka
Wakamatsu Shuhei
Chiyoda Corporation
Griffin Steven P.
Lorusso & Loud
Stickland Jonas N.
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