Chemistry of hydrocarbon compounds – Purification – separation – or recovery – By addition of extraneous agent – e.g. – solvent – etc.
Reexamination Certificate
1999-12-20
2003-06-10
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Purification, separation, or recovery
By addition of extraneous agent, e.g., solvent, etc.
C585S809000, C585S833000, C585S866000
Reexamination Certificate
active
06576806
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for separating C
2
-C
3
olefins from industrial gases.
BACKGROUND OF THE INVENTION
Many industrial processes produce olefin streams within the average carbon number range of C
2
-C
3
. The feedstock may be generated by commercial processes such as the olefinic (ethylene) products of hydrocarbon pyrolysis furnaces. Such hydrocarbon pyrolysis furnaces are typically fed by natural gas liquids, which contain significant amounts of ethane, propane, butane, or gasoline, or fed by naphtha or gas oil. Also the term “steam cracker for production of olefins” is used. In some instances, operators do actually feed olefins to the cracking furnaces such as where they don't have a market for C3, C4, C5 olefins, so the term “olefins steam cracker” could be misunderstood, olefins normally not being a cracker feedstock. Other processes which generate feedstocks containing olefins include streams produced from the light ends (C
4
or less) of any refinery thermal cracker using a vacuum flasher bottoms as the feed; a stream from the light ends (C
4
or less) of any coker using a vacuum flasher bottoms as the feed; any one of the product streams from a fluidized catalytic cracking, (FCC) unit's gas plant receiving the C
4
or less cuts from a crude distillation column; the overhead of a cat cracking unit; or the C
4
or less cut of a fractionation column fed by the product of a FCC Unit.
In many of these process, olefins are separated from impurities and by-products, such as saturated hydrocarbons, sulfur compounds, carbon oxides, and nitrogen containing compounds through costly cryogenic distillation, due to operating the process with expensive refrigeration units. Since the industrial C2-C3 streams are gaseous at room temperature, these streams are first cooled to liquify the ingredients followed by subjecting the liquid stream to a distillation process for separating the olefins from the liquid mixture. Another process to separate impurities, such as acetylenes, from ethylene streams is a solvent extraction. Solvent extraction, however, is not effective for separating olefins from saturated hydrocarbons. It would be desirable to separate out olefins from a wide variety of impurities and by-products, such as saturated hydrocarbons, carbon oxides, and sulfur and nitrogen bearing compounds, present in industrial streams containing olefins in the C
2
-C
4
range, and which does not require the use of cryogenic units to conduct the separation.
U.S. Pat. Nos. 4,946,560, 5,936,136, and 5,942,656 describe processes for the separation of internal olefins from alpha olefins, and linear alpha olefins from 2-branched and/or 3-branched alpha olefins, by contacting a feedstock with an adducting compound such as anthracene or benzanthracene to form an olefin adduct, separating the adduct from the feedstock, dissociating the olefin adduct through heat to produce anthracene and an olefin composition enriched in alpha olefin, and separating out the anthracene from the alpha olefin. This reference does not suggest the desirability or the capability of anthracene to separate C
2
-C
3
olefins contained in industrial streams from a gaseous mixture of C
2
-C
3
olefins, saturated hydrocarbons, carbon oxides, sulfur bearing compounds, and nitrogen bearing compounds.
SUMMARY OF THE INVENTION
This invention relates to a process for treating a feedstock comprising olefins having an average carbon number ranging from, 2-3.5, and non-olefinic compounds, said process comprising the following steps:
a) contacting gaseous feedstock with a linear polyaromatic compound in a reaction zone under conditions effective to form a reaction mixture comprising linear polyaromatic compound-olefin adducts and unreacted gaseous feedstock;
b) separating the olefin adducts from the unreacted gaseous feedstock; and
c) dissociating the olefin adducts to form linear polyaromatic compounds and an olefin enriched composition comprising ethylene, propylene, or mixtures thereof;
whereby the concentration of at least one of the olefins in said olefin enriched composition is enriched over the concentration of the corresponding olefin in the feedstock.
DETAILED DESCRIPTION OF THE INVENTION
As used throughout this specification and in the claims, the term “comprising” means “at least,” such that other unmentioned elements, ingredients, or species are not excluded from the scope of invention.
The feedstock to be treated comprises at least olefins and non-olefinic compounds, wherein the olefins have an average carbon number ranging from 2-3.5, based on a weighted average of moles of olefins present in the feedstock. An olefin means any compound containing at least one carbon-carbon double bond. Except for ethylene and propylene, other olefins present in the feedstock may be linear or branched. Examples of olefins which are present in the feedstock include at least one of ethylene, proplyene, or mixtures thereof or mixtures with other olefins such as butylene and/or pentenes.
The class of non-olefinic compounds generally includes saturated hydrocarbons. Saturated hydrocarbon include paraffins, and may also include other molecules such as cycloparaffins, which may be present in trace quantities. Other non-olefinic compounds typically present in the feedstock include methane, ethane, carbon dioxide, carbon monoxide, hydrogen, and sulfur and/or nitrogen bearing compounds. Examples of sulfur bearing compounds are H
2
S, alkyl mercaptans, CS
2
, and COS. Examples of nitrogen bearing compounds include ammonia, nitrogen, and amines.
The feedstock may be generated by commercial processes such as the product of an olefins (e.g. ethylene) pyrolysis furnaces; an olefins steam cracker; a stream from the light ends (mixtures of C
4
hydrocarbons or less) of any refinery thermal cracker using a vacuum flasher bottoms as the feed; a stream from the light ends (mixtures of C
4
hydrocarbons or less) of any coker using a vacuum flasher bottoms as the feed; any one of the product streams from a cat cracking gas plant receiving the mixture of C
4
hydrocarbons or less cuts from a crude distillation column; the overhead of a cat cracking unit, and/or a catalyst reforming unit; any one of the products from the bottoms of a hydrotreater for removing sulfur compounds; the light butane overhead from a crude distillation column; the mixture of C
4
hydrocarbons or less cut of a fractionation column fed by the product of a cat cracker, or derived by removal of light ends (C
1
-C
4
) in a Fisher-Tropsch product stream.
In one embodiment, the feedstock is a stream used to feed a C
2
splitter fractionation column where ethylene is separated from ethane. The feedstock to a C
2
splitter is derived from the product recovery and purification section of an olefins plant and originates in the radiant zone of the pyrolysis furnaces in the plant where feedstock pyrolysis takes place. Generally, the pyrolysis gases from the radiant zone of the ethylene furnace are separated first in a fractionator into gasoline and lighter fractions as an overhead and heavier than gasoline compounds as the bottoms in a fractionator. The overhead gases are compressed and cooled to form liquids and fed to a de-methanizer system to remove hydrogen and methane as an overhead. The remaining compounds from the bottoms of the de-methanizer are fed to a de-ethanizer to remove and isolate C
2
compounds as an overhead for feedstock to the C2 splitter fractionation column which would be replaced by this invention. Other separation systems may have equipment arranged in a different sequence, or with different or additional equipment. In this embodiment, however, regardless of the separation system employed, the feedstock used for the separation system according to the invention is derived from an ethylene pyrolysis furnace which has been subjected to one or more separations to concentrate a stream containing C
2
compounds, primarily ethylene and ethane. Most of the C
2
feedstock streams contain at least 90 wt. % ethane and ethylene, and even at
Fenouil Laurent Alain
Fong Howard Lam-Ho
Slaugh Lynn Henry
Griffin Walter D.
Shell Oil Company
LandOfFree
Process for separating C2-C3 olefins from industrial gases does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for separating C2-C3 olefins from industrial gases, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for separating C2-C3 olefins from industrial gases will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3109324