Catalyst for converting carbon dioxide to oxygenates and...

Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – Gallium containing

Reexamination Certificate

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C502S064000, C502S067000, C502S346000, C502S353000, 57

Reexamination Certificate

active

06664207

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the conversion of carbon dioxide to oxygenates. In another aspect, the invention concerns a catalyst for converting a feed comprising carbon dioxide and hydrogen into methanol and dimethyl ether.
2. Discussion of Prior Art
Carbon dioxide for industrial use is typically recovered from synthesis gas production, substitute-natural gas production, cracking of hydrocarbons, and natural springs or wells. Although carbon dioxide can be used for numerous purposes such as, for example, refrigeration, carbonating beverages, and as an aerosol propellent, in certain situations it may be more desirable to convert carbon dioxide to other higher-value compounds such as oxygenates.
Oxygenates can be used for a variety of purposes such as, for example, enhancing of motor fuel octane and improving the emissions quality of motor fuel. Methanol and dimethyl ether are two oxygenates which can be of particularly high value. Methanol can be used for a variety of purposes including, for example, as an alternative motor fuel, as an intermediate in the production of high octane ethers (e.g., MTBE), and as a fuel for fuel cell driven vehicles. Dimethyl ether is also useful for a variety of purposes including, for example, as an alternative motor fuel, as a starting material towards the synthesis of various hydrocarbons, as a fuel additive to lower emissions, and as an aerosol propellent.
Although it is known that synthesis gas comprising carbon monoxide, carbon dioxide, and hydrogen can be converted into oxygenates using a copper-containing catalyst, there exists a need for a catalyst which is effective to convert carbon dioxide into oxygenates with increased carbon dioxide conversion as well as increased product selectivity towards methanol and dimethyl ether, particularly dimethyl ether.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the present invention is to provide a catalyst and process for converting carbon dioxide to oxygenates wherein there is an increased carbon dioxide conversion.
A further object of the present invention is to provide a catalyst and process for converting carbon dioxide to oxygenates wherein there is an increased product selectivity towards methanol and dimethyl ether.
A still further object of the present invention is to provide a catalyst and process for converting carbon dioxide to oxygenates wherein there is an enhanced product selectivity towards dimethyl ether versus methanol.
An even further object of the present invention is to provide a catalyst and process for converting carbon dioxide to oxygenates wherein the amount of carbon monoxide produced is minimized.
A yet further object of the present invention is to provide a novel process for preparing a catalyst effective to convert carbon dioxide into oxygenates.
It should be noted that not all of the above-listed objects need be accomplished by the invention claimed herein and other objects and advantages of this invention will be apparent from the following description of the invention and appended claims.
In accordance with one embodiment of the present invention, a catalyst composition is provided. The catalyst composition comprises copper, zinc, aluminum, gallium, and a solid acid.
In accordance with another embodiment of the present invention a catalyst composition for converting carbon dioxide to methanol and dimethyl ether is provided. The catalyst composition comprises reduced-valence copper, zinc oxide, aluminum oxide, gallium oxide, and a zeolite having an acid function.
In accordance with a further embodiment of the present invention, a method of making a catalyst composition is provided. The method comprises the steps of: (a) combining a copper-containing compound, a zinc-containing compound, an aluminum-containing compound, a gallium-containing compound, and a solid acid compound to form a catalyst mixture; (b) calcining the catalyst mixture to form a calcined catalyst; and (c) reducing the calcined catalyst to form a reduced catalyst.
In accordance with a still further embodiment of the present invention, a process for converting a carbon dioxide-containing feed into oxygenates is provided. The process comprises the steps of: (a) contacting the carbon dioxide-containing feed with a catalyst composition comprising copper, zinc, aluminum, gallium, and a solid acid in a reaction zone under reaction conditions sufficient to convert at least a portion of the carbon dioxide-containing feed into oxygenates; and (b) recovering of at least a portion of the oxygenates from the reaction zone.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with the first embodiment of the present invention a catalyst comprising copper, zinc, aluminum, gallium, and a solid acid is provided.
The copper component of the inventive composition can exist in the form of any copper-containing compound such as, for example, elemental copper, copper oxide, and/or a copper oxide precursor. It is preferred for the inventive catalyst composition to contain from about 2 to about 50 weight percent copper based on the total weight of the catalyst composition, more preferably from about 10 to about 35 weight percent copper, most preferably from 20 to 30 weight percent copper. At least a substantial portion of the copper component is preferably present in the inventive catalyst composition in a reduced-valence state. The valence of the copper in the reduced-valence state (i.e., the reduced-valence copper) is less than the valence of copper in its common oxidized state, preferably less than two, most preferably zero. It is preferred that at least about 20 weight percent of the copper present in the inventive catalyst composition be present in the reduced-valence state, more preferably at least about 60 weight percent of the copper is present in the reduced-valence state, and most preferably at least 80 weight percent of the copper is present in the reduced-valence state.
The zinc component can exist in the form of any zinc-containing compound such as, for example, elemental zinc, zinc oxide, and/or a zinc oxide precursor. Preferably, the zinc component comprises zinc oxide. It is preferred for the inventive composition to contain from about 1 to about 40 weight percent zinc based on the total weight of the catalyst composition, more preferably from about 5 to about 30 weight percent zinc, most preferably from 10 to 20 weight percent zinc. The weight ratio of zinc to copper in the inventive catalyst composition is preferably from about 0.01:1 to about 10:1, more preferably from about 0.1:1 to about 5:1, and most preferably from 0.4:1 to 0.8:1.
The aluminum component can exist in the form of any aluminum-containing compound such as, for example, elemental aluminum, aluminum oxide, and/or an aluminum oxide precursor. Preferably, the aluminum component comprises aluminum oxide. It is preferred for the inventive catalyst composition to contain from about 0.5 to about 25 weight percent aluminum based on the total weight of the catalyst composition, more preferably from about 1 to about 15 weight percent aluminum, and most preferably from 2 to 5 weight percent aluminum. The weight ratio of aluminum to copper in the inventive catalyst composition is preferably from about 0.01:1 to about 5:1, more preferably from about 0.05:1 to about 1:1, and most preferably from 0.1:1 to 0.2:1.
The gallium component can exist in the form of any gallium-containing compound such as, for example, elemental gallium, gallium oxide, and/or a gallium oxide precursor. Preferably, the gallium component comprises gallium oxide. It is preferred for the inventive catalyst composition to contain from about 0.1 to about 15 weight percent gallium based on the total weight of the inventive catalyst composition, more preferably from about 0.5 to about 10 weight percent gallium, and most preferably from 1 to 3 weight percent gallium. The weight ratio of gallium to copper in the inventive catalyst composition is preferably from about 0.005:1 to about 5:1, more preferably from

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