Selective hydrogenation process and catalyst therefor

Details Selective hydrogenation process and catalyst therefor Selective hydrogenation process and catalyst therefor

2000-01-14

2002-05-14

Yildirim, Bekir L. (Department: 1764)

Chemistry of hydrocarbon compounds

Adding hydrogen to unsaturated bond of hydrocarbon, i.e.,...

Hydrocarbon is contaminant in desired hydrocarbon

C585S258000, C585S259000

Reexamination Certificate

active

06388150

ABSTRACT:

This invention relates to the selective hydrogenation of impurities in a feed containing hydrocarbons. More particularly, this invention relates to a process for selectively hydrogenating compounds having a triple bond as opposed to compounds having any double bond, and/or selectively hydrogenating compounds having two double bonds as opposed to compounds having a single double bond, and/or selectively hydrogenating compounds having a triple bond and compounds having two double bonds as opposed to compounds having a single double bond, and/or selectively hydrogenating compounds that contain cumulated double bonds as opposed to those where the double bonds are separated by one or more single bonds. Such reactions include, but are not limited to, the selective hydrogenation of acetylenic and/or dienic impurities in a feed containing at least one monoolefin, such as, for example, the selective hydrogenation of methylacetylene and propadiene (or MAPD) in a feed containing propylene; the selective hydrogenation of butadiene as opposed to butene; the selective hydrogenation of vinyl and ethyl acetylene and 1,2-butadiene in a feed containing 1,3-butadiene; the selective hydrogenation of acetylene as opposed to ethylene; and the selective hydrogenation of C
5
and C
6
diolefins as opposed to C
5
and C
6
monoolefins.
The present invention, in another embodiment, also relates to the selective hydrogenation of olefins and dienes in a stream containing olefins, dienes, and aromatics.
Although the scope of the present invention is not intended to be limited to any specific selective hydrogenation, the invention will be described with particularity with respect to the selective hydrogenation of acetylenic and/or dienic impurities in a feed containing at least one monoolefin.
In the petrochemical industry, there are produced streams which contain one or more monoolefins, and which also contain, as impurities, acetylenic compounds and/or dienes. For example, propylene and/or butene cuts obtained from various pyrolysis processes, particularly pyrolysis in the presence of steam, contain, as impurities, acetylenic compounds and/or dienes, and in general, both acetylenic compounds and dienes. Acetylenic impurities include acetylene, methylacetylene, and diacetylene, and dienic impurities include propadiene, 1,2-butadiene, and 1,3-butadiene. In general, a propylene stream recovered from a steam pyrolysis process contains both methylacetylene and propadiene impurities.
In the petrochemical industry, such a stream is subjected to a selective hydrogenation process in order to hydrogenate the acetylenic and/or dienic impurities, while minimizing hydrogenation of the desired monoolefin. Such a process may be accomplished by a catalytic hydrogenation, using a supported catalyst, such as, for example, a noble metal catalyst, such as a palladium catalyst, supported on a suitable support.
The present invention is directed to an improved method and catalyst for the selective hydrogenation of impurities in a feed containing hydrocarbons.
In accordance with an aspect of the present invention, there is provided a process for selectively hydrogenating one or more impurities in a feed containing hydrocarbons. The process comprises hydrogenating the impurity(ies) in the presence of a selective hydrogenation catalyst supported on a particulate support. The supported catalyst is supported on a mesh-like structure. The term “supported on the mesh” as used herein includes coating the supported catalyst on the mesh as well as entrapping the supported catalyst in the interstices of the mesh. The catalyst that is supported on the mesh, in one embodiment, is comprised of a catalyst supported on a particulate support with the supported catalyst being supported on the mesh. In another embodiment, the catalyst is supported on a particulate support that is supported on one or more other supports that are supported on the mesh.
In one embodiment, the process for selectively hydrogenating an impurity is a process for selectively hydrogenating compounds having a triple bond as opposed to compounds having any double bond and/or selectively hydrogenating compounds having two double bonds as opposed to a single double bond. Representative examples of such selective hydrogenation reactions include, but are not limited to, the selective hydrogenation of acetylenic and/or dienic impurities in a feed containing at least one monoolefin, such as, for example, the selective hydrogenation of methylacetylene and propadiene (MAPD) in a feed containing propylene; the selective hydrogenation of butadiene as opposed to butene; the selective hydrogenation of acetylene as opposed to ethylene; and the selective hydrogenation of C
5
and C
6
diolefins as opposed to C
5
and C
6
monoolefins. Other reactions include selectively hydrogenating compounds having a triple bond and those that contain cumulated double bonds as opposed to those where the double bonds are separated by one or more single bonds. In one embodiment, the selective hydrogenation is a process for selectively hydrogenating ethyl and vinyl acetylene and 1,2-butadiene as opposed to 1,3-butadiene.
In one embodiment, the selective hydrogenation is a process for selectively hydrogenating an impurity selected from the group consisting of acetylene compounds, dienes, and mixtures thereof in a feed containing at least one monoolefin and the impurity. The impurity is hydrogenated selectively in the presence of a selective hydrogenation catalyst supported on a particulate support. The supported catalyst is supported on a mesh-like structure.
In another embodiment, the process for selectively hydrogenating an impurity is a process for selectively hydrogenating dienes and styrene in a stream containing dienes, styrene, olefins, and aromatics. An example of such a feed is a pyrolysis gasoline feed. The selective hydrogenation is effected in the presence of a selective hydrogenation catalyst supported on a particulate support, wherein the supported catalyst is supported on a mesh-like structure as described herein.
More particularly, the mesh-like material is comprised of fibers or wires, such as a wire or fiber mesh, a metal felt or gauze, metal fiber filter or the like. The mesh-like structure may be comprised of a single layer, or may include more than one layer of wires; e.g., a knitted wire structure or a woven wire structure and preferably is comprised of a plurality of layers of wires or fibers to form a three dimensional network of materials. In a preferred embodiment, the support structure is comprised of a plurality of layers of fibers that are oriented randomly in the layers. One or more metals may be used in producing a metal mesh Alternatively the mesh fibers may be formed from or include materials other than metals alone or in combination with metals; e.g. carbon or metal oxides or a ceramic. In one embodiment, the mesh includes a metal. In the case where the mesh supports the catalyst, the material which forms the mesh, in one embodiment, is non-catalytic with respect to the selective hydrogenation of impurities in a hydrogenation feed.
In a preferred embodiment wherein the mesh-like structure is comprised of a plurality of layers of fibers to form the three dimensional network of materials, the thickness of such support is at least five microns, and generally does not exceed ten millimeters. In accordance with a preferred embodiment, the thickness of the network is at least 50 microns and more preferably at least 100 microns and generally does not exceed 2 millimeters.
In general, the thickness or diameter of the fibers which form the plurality of layers of fibers is less than about 500 microns, preferably less than about 150 microns and more preferably less than about 30 microns. In a preferred embodiment, the thickness or diameter of the fibers is from about 8 to about 25 microns.
The three dimensional mesh-like structure may be produced as described in U.S. Pat. No. 5,304,330, 5,080,962; 5,102,745 or 5,096,663. It is to be understood, however, that such mesh-like structur

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