Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2000-08-15
2003-10-21
Yildirim, Bekir L. (Department: 1764)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S223000, C502S347000
Reexamination Certificate
active
06635600
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a supported noble metal catalyst composition and to a process for selectively hydrogenating a highly unsaturated hydrocarbon employing a supported noble metal catalyst composition.
BACKGROUND OF THE INVENTION
Catalysts comprising palladium and an inorganic support are known catalysts for the hydrogenation of polyenes and/or alkynes. Even though these catalysts are effective hydrogenation catalysts, they ten to produce green oil by oligomerizing alkenes, polyenes, and/or alkynes. Green oil, as used herein, refers to molecules having 6 or more carbon atoms per molecule and is undesirable in the production of an alkene because it fouls the hydrogenation catalyst which in turn deactivates the catalyst. The deactivation process can lower the activity and selectivity of the catalyst. Therefore, there is an ever present need for further improvements in the selective hydrogenation process for converting a highly unsaturated hydrocarbon to a less unsaturated hydrocarbon and to achieve enhanced selectivity to the less unsaturated hydrocarbon, or increased catalyst life, or both. Accordingly, the development of a modified supported palladium catalyst composition and its use in processes for the selective hydrogenation of highly unsaturated hydrocarbons such as diolefins (alkadienes) or alkynes to less unsaturated hydrocarbons such as monoolefins (alkenes) would be a significant contribution to the art.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a palladium-containing catalyst composition which can be useful as a catalyst in the selective hydrogenation of a highly unsaturated hydrocarbon such as a diolefin and/or alkyne to a less unsaturated hydrocarbon such as a monoolefin. It is another object of this invention to employ this catalyst composition in the selective hydrogenation of highly unsaturated hydrocarbons such as diolefins or alkynes to monoolefins. An advantage of this invention is the increased or enhanced selectivity to a desired product and the decreased production of oligomers which form green oils, thereby increasing the life cycle of the catalyst. Other objects and advantages will become more apparent as the invention is more fully disclosed hereinbelow.
According to a first embodiment of this invention, a catalyst composition is provided which comprises, consists essentially of, or consists of palladium, an inorganic support material, and a selectivity enhancer which is silver, phosphorus, sulfur, or combinations of two or more thereof. The inorganic support can be a spinel, alumina, silica, titania, zirconia, an aluminosilicate, an aluminate such as zinc aluminate, magnesium aluminate, calcium aluminate, or combinations of two or more thereof.
According to a second embodiment this invention, a process which can be used for selectively hydrogenating a highly unsaturated hydrocarbon to a less unsaturated hydrocarbon is provided. The process comprises contacting a highly unsaturated hydrocarbon with hydrogen, in the presence of a catalyst composition, under a condition sufficient to effect a selective hydrogenation of the highly unsaturated hydrocarbon. The catalyst composition can be the same as the composition disclosed in the first embodiment of this invention.
DETAILED DESCRIPTION OF THE INVENTION
As used in the present invention, the term “fluid” denotes gas, liquid, or combination thereof. The term “selectivity enhancer” denotes an element or compound which enhances the selectivity to an alkene, decreases the selectivity to an alkane, or decreases the selectivity to an undesirable product such as green oils when the composition of the invention is employed as a catalyst in a selective hydrogenation process disclosed in this invention. The term “substantial” or “substantially” generally means more than trivial. A “saturated hydrocarbon” is referred to as any hydrocarbon which does not contain any carbon to carbon multiple bonds. An “unsaturated hydrocarbon” as used in this invention is a hydrocarbon having at least one double bond or triple bond between carbon atoms in the molecule. Example of saturated hydrocarbons include, but are not limited to, ethane, propane, butanes, pentanes, hexanes, octanes, decanes, naphtha, and combinations of any two or more thereof. Examples of unsaturated hydrocarbons include, but are not limited to, monoolefins such as ethylene, propylene, butenes, pentenes, hexenes, octenes, and decenes; aromatic compounds such as benzene and naphthalene; alkynes such as acetylene, propyne, and butynes; diolefins such as propadiene, butadienes, pentadienes (including isoprene), hexadienes, octadienes, and decadienes; and combinations of two or more thereof. The term “highly unsaturated hydrocarbon” refers to a hydrocarbon which contains a triple bond or two or more double bonds in a molecule. The term “less unsaturated hydrocarbon” refer to a hydrocarbon in which the triple bond in the highly unsaturated hydrocarbon is hydrogenated to a double bond or a hydrocarbon in which the number of double bonds is one less, or at least one less, than that in the highly unsaturated hydrocarbon. The term “selective hydrogenation” is referred to as a hydrogenation process which converts a highly unsaturated hydrocarbon such as an alkyne or a diolefin to a less unsaturated hydrocarbon such as a monoolefin without hydrogenating the less unsaturated hydrocarbon to a more saturated hydrocarbon or a saturated hydrocarbon such as alkane.
The composition of this invention comprises, consists essentially of, or consists of (a) palladium such as palladium metal, palladium oxide, or combinations thereof in which the palladium can be present as a “skin” distributed on the surface of an inorganic support, (b) an inorganic support selected from the group consisting of alumina, silica, titania, zirconia, aluminosilicates (clays and/or zeolites), a spinel such as zinc aluminate, zinc titanate and magnesium aluminate, and combinations of two or more thereof, (c) a selectivity enhancer selected from the group consisting of silver, silver compounds, phosphorus, sulfur, phosphorus compounds, sulfur compounds, potassium, potassium compounds, and combinations of two or more thereof, and optionally (d) a fluorine- or fluoride-containing compound. Examples of suitable selectivity enhancer compounds include, but are not limited to, silver, silver nitrate, silver chloride, potassium phosphate, sodium phosphate, ammonium phosphate, sodium sulfate, potassium sulfate, ammonium sulfate, and combinations of two or more thereof. The term “phosphate” also includes dibasic and monobasic phosphates. Examples of suitable fluorine- or fluoride-containing compounds include, but are not limited to, non-alkali metal fluorides such as ammonium fluoride, hydrogen fluoride, and ammonium hydrogen fluoride; alkali metal fluorides such as sodium fluoride, potassium fluoride rubidium fluoride, and cesium fluoride; and combinations of two or more thereof.
Generally, the composition can contain about 0.001 to about 3, preferably about 0.001 to about 2 weight % Pd; about 0.002 to about 10, preferably about 0.01 to about 5 weight % each selectivity enhancer; optionally about 0.002 to about 10, preferably about 0.01 to about 5 weight % fluorine; and the rest being inorganic support. The composition can have any suitable shape such as spherical, cylindrical, trilobal, or combinations of two or more thereof. The preferred shape is either spherical or cylindrical. The particles of this catalyst generally have a size of about 1 to about 10 mm, preferably about 2 to about 6 mm. Generally the surface area of the catalyst as measured by the BET method (Brunauer, Emmett and Teller) employing N
2
is 0.5 to about 200, preferably about 1 to about 100 m
2
/g.
The composition can be produced by any suitable means known to one skilled in the art. For example, the components (a) and (c) as well as the optional component (d) can be deposited onto and/or incorporated into the inorganic support by any suitable means. For instance, the selectivity enhancer(s)
Bergmeister Joseph J.
Kimble James B.
Carroll Rodney B.
Conley & Rose, P.C.
Phillips Petroleum Company
Yildirim Bekir L.
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