Hydrocarbon hydrogenation catalyst and process

Details Hydrocarbon hydrogenation catalyst and process Hydrocarbon hydrogenation catalyst and process

2001-12-21

2004-09-21

Yildirim, Bekir L. (Department: 1764)

Chemistry of hydrocarbon compounds

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

Partial

C585S259000, C208S144000

Reexamination Certificate

active

06794552

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a supported metal catalyst composition, a process of making such supported metal catalyst composition, and to a process of using such supported metal catalyst composition for hydrogenating a highly unsaturated hydrocarbon.
It is known to one skilled in the art that a less unsaturated hydrocarbon compound can be produced by a thermal cracking process. For example, a fluid stream containing a saturated hydrocarbon such as, for example, ethane, propane, butane, pentane, naphtha, and the like and combinations thereof can be fed into a thermal (or pyrolytic) cracking furnace. Within the furnace, the saturated hydrocarbon is converted to a less unsaturated hydrocarbon compound such as, for example, ethylene or propylene. Such less unsaturated hydrocarbons are an important class of chemicals that find a variety of industrial uses. For example, ethylene can be used as a monomer or comonomer for producing a polyolefin. Other uses of unsaturated hydrocarbons are well known to one skilled in the art.
However, such less unsaturated hydrocarbon produced by a thermal cracking process generally contains an appreciable amount of less desirable highly unsaturated hydrocarbon(s) such as alkyne(s) or diolefin(s). For example, ethylene produced by thermal cracking of ethane is generally contaminated with a highly unsaturated hydrocarbon, such as acetylene, which must be selectively hydrogenated to a less unsaturated hydrocarbon, such as ethylene, but not to a saturated hydrocarbon such as ethane, in a hydrogenation reaction.
In addition, catalysts comprising palladium and an inorganic support, such as alumina, are known catalysts for the hydrogenation of highly unsaturated hydrocarbons such as alkynes and/or diolefins. In the case of the selective hydrogenation of acetylene to ethylene, a palladium and silver catalyst supported on alumina can be employed. See for example U.S. Pat. No. 4,404,124 and U.S. Pat. No. 4,484,015, the disclosures of which are incorporated herein by reference. The operating temperature for this hydrogenation process is selected such that essentially all highly unsaturated hydrocarbon such as alkyne (e.g., acetylene) is hydrogenated to its corresponding less unsaturated hydrocarbon such as alkene (e.g., ethylene) thereby removing the alkyne from the product stream while only an insignificant amount of alkene is hydrogenated to a saturated hydrocarbon such as alkane (e.g., ethane). Such selective hydrogenation process minimizes the loss of desired less unsaturated hydrocarbons and, in the front-end and total cracked gas processes, avoids a “runaway” reaction which is difficult to control, as has been pointed out in the above-identified patents.
It is also generally known to those skilled in the art that impurities, such as carbon monoxide, and sulfur impurities, such H
2
S, COS, mercaptans and organic sulfides, which are present in an alkyne-containing feed or product stream can poison and deactivate a palladium-containing catalyst. For example, carbon monoxide is well known to temporarily poison or inactivate such hydrogenation catalyst. It is also generally known by those skilled in the art that a sulfur impurity such as a sulfur compound (such as H
2
S, COS, mercaptans, and organic sulfides), when present during the hydrogenation of highly unsaturated hydrocarbons such as diolefins (alkadienes) or alkynes to less unsaturated hydrocarbons such as monoolefins (alkenes), can poison and deactivate hydrogenation catalysts. This is especially true in a depropanizer hydrogenation process because the feed stream from the depropanizer being sent to the acetylene removal unit (also referred to as “ARU”) of such depropanizer hydrogenation process typically contains low levels of a sulfur compound(s) with the possibility of transient spikes in the level of such sulfur compound(s). Thus, the development of a catalyst composition and its use in processes for the hydrogenation of highly unsaturated hydrocarbons such as diolefins (alkadienes) or alkynes to less unsaturated hydrocarbons such as monoolefins (alkenes) in the presence of a sulfur impurity such as a sulfur compound would also be a significant contribution to the art and to the economy.
A palladium-containing “skin” catalyst in which palladium is distributed on the surface or “skin” of the catalyst has been developed which is known to be more selective and active than a non-skin catalyst in converting acetylene in an ethylene stream to ethylene. See for example, U.S. Pat. No. 4,484,015. It is known that the catalyst selectivity is determined, in part, by the skin thickness. Generally, catalyst selectivity decreases as the skin thickness increases. There is therefore an ever-increasing need to develop a catalyst having a better “skin” on the catalyst for a better selective hydrogenation of a highly unsaturated hydrocarbon, such as an alkyne, to a less unsaturated hydrocarbon, such as an alkene, without further hydrogenation to a saturated hydrocarbon, such as an alkane.
Palladium supported on alumina has been successfully used in dry hydrogenation processes for many years. However, in some processes such as the so-called “total cracked gas” process in which the steam is not removed from the olefins stream, the selective hydrogenation of a highly unsaturated hydrocarbon, such as an alkyne, to a less unsaturated hydrocarbon, such as an alkene, must be accomplished in the presence of steam. In such process(es), the alumina supported catalyst may have a much shorter life because alumina is not stable in steam. Therefore, there is also an increasing need to develop a palladium-containing catalyst on a steam-stable support.
As such, development of an improved palladium catalyst and a process therewith in the selective hydrogenation of a highly unsaturated hydrocarbon, such as an alkyne, to a less unsaturated hydrocarbon, such as an alkene, in the presence of an impurity would be a significant contribution to the art and to the economy.
It is also generally known that catalysts having a metal aluminate support, such as a zinc aluminate support, can be used in the selective hydrogenation and dehydrogenation of hydrocarbons. In general, prior art processes to produce such metal aluminate support typically involve physically mixing a metal component, such as metal oxide, and an aluminum component, such as aluminum oxide, followed by drying and calcining to produce a metal aluminate catalyst support containing a metal aluminate such as a zinc aluminate, also referred to as a zinc spinel. Another common process of producing such metal aluminate catalyst support comprises coprecipitating an aqueous solution of a metal component, such as metal nitrate, and an aqueous solution of an aluminum component, such as aluminum nitrate, followed by drying and calcining such as the process disclosed in U.S. Pat. No. 3,641,182. However, these processes are costly and time-consuming. Consequently, a process to produce a metal aluminate catalyst support, which does not involve physical mixing or coprecipitation, which can be incorporated with palladium and a catalyst component comprising either silver, an alkali metal compound, or both silver and an alkali metal compound, and which can be used in the selective hydrogenation of a highly unsaturated hydrocarbon, such as an alkyne, to a less unsaturated hydrocarbon, such as an alkene, in the presence of an impurity would also be of significant contribution to the art and to the economy.
SUMMARY OF THE INVENTION
An object of this invention is to provide a catalyst composition that can be used for selectively hydrogenating a highly unsaturated hydrocarbon, such as an alkyne, to a less unsaturated hydrocarbon, such as an alkene. Such catalyst composition can be useful as a catalyst in the hydrogenation of a highly unsaturated hydrocarbon such as a diolefin and/or alkyne to a less unsaturated hydrocarbon such as a monoolefin.
Another object of this invention is to provide a palladium-containing catalyst composition wherein the palladium is better distribute

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