U.S. patent application number 13/851509 was filed with the patent office on 2014-10-02 for process for regenerating ionic liquids by adding light hydrocarbon stream.
This patent application is currently assigned to UOP LLC. The applicant listed for this patent is UOP LLC. Invention is credited to Alakananda Bhattacharyya, Rajeswar R. Gattupalli, Beckay J. Mezza, Massimo Sangalli.
Application Number | 20140291208 13/851509 |
Document ID | / |
Family ID | 51619764 |
Filed Date | 2014-10-02 |
United States Patent
Application |
20140291208 |
Kind Code |
A1 |
Gattupalli; Rajeswar R. ; et
al. |
October 2, 2014 |
PROCESS FOR REGENERATING IONIC LIQUIDS BY ADDING LIGHT HYDROCARBON
STREAM
Abstract
A process for removing at least one impurity from a hydrocarbon
feed such as vacuum gas oil in which the process includes the steps
of contacting the feed with a hydrocarbon-immiscible phosphonium
ionic liquid to produce a hydrocarbon and hydrocarbon-immiscible
phosphonium ionic liquid mixture, and separating the mixture to
produce a hydrocarbon effluent having a reduced impurity content
relative to the hydrocarbon feed.
Inventors: |
Gattupalli; Rajeswar R.;
(Arlington Heights, IL) ; Sangalli; Massimo; (Des
Plaines, IL) ; Mezza; Beckay J.; (Arlington Heights,
IL) ; Bhattacharyya; Alakananda; (Glen Ellyn,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UOP LLC |
Des Plaines |
IL |
US |
|
|
Assignee: |
UOP LLC
Des Plaines
IL
|
Family ID: |
51619764 |
Appl. No.: |
13/851509 |
Filed: |
March 27, 2013 |
Current U.S.
Class: |
208/292 ;
252/364 |
Current CPC
Class: |
C10G 21/28 20130101;
C10G 21/27 20130101; C10G 2300/201 20130101 |
Class at
Publication: |
208/292 ;
252/364 |
International
Class: |
C10G 21/28 20060101
C10G021/28 |
Claims
1. A process for removing at least one impurity from a hydrocarbon
stream comprising: (a) contacting a hydrocarbon stream with a
hydrocarbon-immiscible phosphonium ionic liquid to produce a
mixture comprising the hydrocarbon and the hydrocarbon-immiscible
phosphonium ionic liquid; (b) separating the mixture to produce a
hydrocarbon product and a hydrocarbon-immiscible phosphonium ionic
liquid effluent, the hydrocarbon-immiscible phosphonium ionic
liquid effluent comprising at least one hydrocarbon impurity; and
(c) contacting the hydrocarbon-immiscible phosphonium ionic liquid
effluent with water and with a light hydrocarbon stream, separating
said hydrocarbon-immiscible phosphonium ionic liquid and said water
from the light hydrocarbon stream and the at least one hydrocarbon
impurity to produce an extract stream comprising the light
hydrocarbon stream and the at least one hydrocarbon impurity and a
separate stream comprising said hydrocarbon-immiscible phosphonium
ionic liquid and water.
2. The process of claim 1 wherein the hydrocarbon stream has a
specific gravity from about 0.8 to 1.2.
3. The process of claim 1 wherein said light hydrocarbon stream is
selected from the group of hydrocarbons having a density lower than
the water or the ionic liquid.
4. The process of claim 1 wherein said hydrocarbon stream is
selected from the group consisting of consisting of naphtha,
diesel, light cycle oil, benzene, kerosene, and toluene.
5. The process of claim 1 wherein the extract stream comprising the
light hydrocarbon stream and the at least one hydrocarbon impurity
has a specific gravity difference of at least 0.01 than a mixture
of said hydrocarbon-immiscible phosphonium ionic liquid and said
water.
6. The process of claim 1 wherein the hydrocarbon stream comprises
a vacuum gas oil.
7. The process of claim 1 wherein the hydrocarbon-immiscible
phosphonium ionic liquid comprises at least one ionic liquid from
at least one of tetraalkylphosphonium dialkylphosphates,
tetraalkylphosphonium dialkyl phosphinates, tetraalkylphosphonium
phosphates, tetraalkylphosphonium tosylates, tetraalkylphosphonium
sulfates, tetraalkylphosphonium sulfonates, tetraalkylphosphonium
carbonates, tetraalkylphosphonium metalates, oxometalates,
tetraalkylphosphonium mixed metalates, tetraalkylphosphonium
polyoxometalates, and tetraalkylphosphonium halides.
8. The process of claim 1 wherein the hydrocarbon-immiscible
phosphonium ionic liquid comprises at least one of
trihexyl(tetradecyl)phosphonium chloride,
trihexyl(tetradecyl)phosphonium bromide,
tributyl(methyl)phosphonium bromide, tributyl(methyl)phosphonium
chloride, tributyl(hexyl)phosphonium bromide,
tributyl(hexyl)phosphonium chloride, tributyl(octyl)phosphonium
bromide, tributyl(octyl)phosphonium chloride,
tributyl(decyl)phosphonium bromide, tributyl(decyl)phosphonium
chloride, tetrabutylphosphonium bromide, tetrabutylphosphonium
chloride, triisobutyl(methyl)phosphonium tosylate,
tributyl(methyl)phosphonium methylsulfate,
tributyl(ethyl)phosphonium diethylphosphate, and
tetrabutylphosphonium methanesulfonate.
9. The process of claim 1 further comprising separating said
hydrocarbon-immiscible phosphonium ionic liquid and water.
10. The process of claim 1 further comprising separating said light
hydrocarbon stream and said at least one hydrocarbon impurity
11. The process of claim 1 wherein the ratio of the hydrocarbon
stream to the hydrocarbon-immiscible phosphonium ionic liquid in
the mixture ranges from about 1:1000 to about 1000:1 on a weight
basis.
12. A process for regenerating an ionic liquid comprising sending a
mixture of an ionic liquid, water and a hydrocarbon extract
containing impurities to a regeneration unit, adding a quantity of
a light hydrocarbon having a lower specific gravity than said
mixture, and removing said light hydrocarbon together with said
hydrocarbon extract containing impurities.
13. The process of claim 12 wherein said light hydrocarbon is
selected from the group consisting of naphtha, kerosene, light
cycle oil, benzene and toluene.
14. The process of claim 12 wherein the hydrocarbon stream
comprises a vacuum gas oil.
15. The process of claim 12 wherein the hydrocarbon-immiscible
phosphonium ionic liquid comprises at least one ionic liquid from
at least one of tetraalkylphosphonium dialkylphosphates,
tetraalkylphosphonium dialkyl phosphinates, tetraalkylphosphonium
phosphates, tetraalkylphosphonium tosylates, tetraalkylphosphonium
sulfates, tetraalkylphosphonium sulfonates, tetraalkylphosphonium
carbonates, tetraalkylphosphonium metalates, oxometalates,
tetraalkylphosphonium mixed metalates, tetraalkylphosphonium
polyoxometalates, and tetraalkylphosphonium halides.
16. The process of claim 12 wherein the hydrocarbon-immiscible
phosphonium ionic liquid comprises at least one of
trihexyl(tetradecyl)phosphonium chloride,
trihexyl(tetradecyl)phosphonium bromide,
tributyl(methyl)phosphonium bromide, tributyl(methyl)phosphonium
chloride, tributyl(hexyl)phosphonium bromide,
tributyl(hexyl)phosphonium chloride, tributyl(octyl)phosphonium
bromide, tributyl(octyl)phosphonium chloride,
tributyl(decyl)phosphonium bromide, tributyl(decyl)phosphonium
chloride, tetrabutylphosphonium bromide, tetrabutylphosphonium
chloride, triisobutyl(methyl)phosphonium tosylate,
tributyl(methyl)phosphonium methylsulfate,
tributyl(ethyl)phosphonium diethylphosphate, and
tetrabutylphosphonium methanesulfonate.
17. The process of claim 12 further comprising separating said
hydrocarbon-immiscible phosphonium ionic liquid and water.
18. The process of claim 12 further comprising separating said
light hydrocarbon stream and said at least one hydrocarbon
impurity.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to processes for regenerating ionic
liquids that are used in decontamination of hydrocarbon streams.
More particularly, the invention relates to process conditions
where the hydrocarbon stream has a density that is close to the
density of an ionic liquid/water mixture and the use of a lower
density hydrocarbon to facilitate the removal of contaminants from
the ionic liquid/water mixture.
[0002] Ionic liquids have many different applications in the
refining industry. For example, they can be used as a solvent to
decontaminate a hydrocarbon stream that feeds into reactors such as
a fluidized catalytic cracking unit (FCC), a hydroprocessing unit
or a hydrocracking unit. During the decontamination process, the
ionic liquid extracts the contaminants and forms two phases--a
clean hydrocarbon phase and a dirty ionic liquid phase comprising
ionic liquid plus contaminants that are mostly hydrocarbons such as
nitrogen, sulfur, or metal containing hydrocarbons and certain
aromatic compounds. Since ionic liquids are usually expensive to
replace, they need to be regenerated for recycling back to the
extraction or contaminant removal step. To separate ionic liquids
from the hydrocarbon impurities, water at typically a 1:1 ionic
liquid/water ratio is added to the mixture. Ionic liquid has more
affinity towards water than the hydrocarbon impurities so that the
ionic liquid rejects the hydrocarbon impurities and forms a
separate phase with water. The hydrocarbon impurities are then
separated from the ionic liquid/water phase as the hydrocarbon
impurity stream and the water is boiled off to regenerate the ionic
liquid. However, it has now been found that, if the density of the
hydrocarbon impurity stream is close to the density of the ionic
liquid/water phase then the separation of the hydrocarbon impurity
stream from the ionic liquid/water phase becomes difficult.
[0003] Hydrocarbon streams may be converted into higher value
hydrocarbon fractions such as diesel fuel, jet fuel, naphtha,
gasoline, and other lower boiling fractions in refining processes
such as hydrocracking and fluid catalytic cracking (FCC). However,
hydrocarbon streams having higher amounts of nitrogen are more
difficult to convert. For example, the degree of conversion,
product yields, catalyst deactivation, and/or ability to meet
product quality specifications may be adversely affected by the
nitrogen content of the feed stream. It is known to reduce the
nitrogen content of vacuum gas oil (VGO) by catalytic hydrogenation
reactions such as in a hydrotreating process unit. The nitrogen
that is removed is often part of a hydrocarbon.
[0004] There are other hydrocarbons and mixtures of hydrocarbons
that have a similar need to remove nitrogen content and other
impurities such as sulfur compounds, or metals. Treatment of such
other hydrocarbons with ionic liquids is within the scope of the
present invention.
[0005] Various processes using ionic liquids to remove sulfur and
nitrogen compounds from hydrocarbon fractions are also known. U.S.
Pat. No. 7,001,504 B2 discloses a process for the removal of
organosulfur compounds from hydrocarbon materials which includes
contacting an ionic liquid with a hydrocarbon material to extract
sulfur containing compounds into the ionic liquid. U.S. Pat. No.
7,553,406 B2 discloses a process for removing polarizable
impurities from hydrocarbons and mixtures of hydrocarbons using
ionic liquids as an extraction medium. U.S. Pat. No. 7,553,406 B2
also discloses that different ionic liquids show different
extractive properties for different polarizable compounds.
[0006] This invention is related to regenerating the ionic liquid
from the ionic liquid/hydrocarbon mixture by adding water and a
light hydrocarbon stream to assist with the removal of hydrocarbon
impurities from the ionic liquid.
SUMMARY OF THE INVENTION
[0007] Water and a light hydrocarbon stream such as
naphtha/kerosene/LCO or any other hydrocarbon which is miscible
with the hydrocarbon feed and/or the extracted hydrocarbon
impurities and has a density lower than water or the ionic liquid
is added to the ionic liquid/hydrocarbon impurities mixture to
regenerate the ionic liquid from the ionic liquid/hydrocarbon
impurities mixture and to also increase the density difference
between the ionic liquid phase and the hydrocarbon phase. In an
embodiment water is added to the ionic liquid/extracted hydrocarbon
mixture before the light hydrocarbon stream is added. The density
difference between the hydrocarbon and ionic liquid phase will help
in the separation of the ionic liquid phase in a conventional
mixer-settler. The hydrocarbon phase (lighter phase) can be sent to
an evaporator or other well known operations such as a steam
stripping column to separate the light hydrocarbon from the
hydrocarbon impurities and the separated light hydrocarbon can be
recycled back to the regeneration step.
[0008] In an embodiment, the invention is a process for removing
nitrogen compounds and other impurities from a hydrocarbon feed
comprising contacting the hydrocarbon with a hydrocarbon-immiscible
phosphonium ionic liquid to produce a hydrocarbon and
hydrocarbon--immiscible phosphonium ionic liquid mixture, and
separating the mixture to produce a hydrocarbon effluent and a
hydrocarbon-immiscible phosphonium ionic liquid effluent comprising
the nitrogen compound. The hydrocarbon-immiscible phosphonium ionic
liquid effluent is mixed with water to separate the hydrocarbon
containing impurities from the ionic liquid. In addition, a light
hydrocarbon such as naphtha, light cycle oil, kerosene or benzene
is added to this mixture to separate the hydrocarbon containing
impurities from the ionic liquid since such separations are
difficult to achieve when the ionic liquid, water and hydrocarbon
containing impurities have essentially the same density. The light
hydrocarbon that is added has a lower density than water, the ionic
liquid or mixtures thereof.
[0009] In an embodiment, the hydrocarbon-immiscible phosphonium
ionic liquid comprises at least one ionic liquid from at least one
of tetraalkylphosphonium dialkylphosphates, tetraalkylphosphonium
dialkyl phosphinates, tetraalkylphosphonium phosphates,
tetraalkylphosphonium tosylates, tetraalkylphosphonium sulfates,
tetraalkylphosphonium sulfonates, tetraalkylphosphonium carbonates,
tetraalkylphosphonium metalates, oxometalates,
tetraalkylphosphonium mixed metalates, tetraalkylphosphonium
polyoxometalates, and tetraalkylphosphonium halides. In another
embodiment, the hydrocarbon-immiscible phosphonium ionic liquid
comprises at least one of trihexyl(tetradecyl)phosphonium chloride,
trihexyl(tetradecyl)phosphonium bromide,
tributyl(methyl)phosphonium bromide, tributyl(methyl)phosphonium
chloride, tributyl(hexyl)phosphonium bromide,
tributyl(hexyl)phosphonium chloride, tributyl(octyl)phosphonium
bromide, tributyl(octyl)phosphonium chloride,
tributyl(decyl)phosphonium bromide, tributyl(decyl)phosphonium
chloride, tetrabutylphosphonium bromide, tetrabutylphosphonium
chloride, triisobutyl(methyl)phosphonium tosylate,
tributyl(methyl)phosphonium methylsulfate,
tributyl(ethyl)phosphonium diethylphosphate, and
tetrabutylphosphonium methanesulfonate.
BRIEF DESCRIPTION OF THE DRAWING
[0010] The FIGURE shows the flow scheme of the present invention in
which a light hydrocarbon stream is employed to separate
hydrocarbon wastes from ionic liquid/water.
DETAILED DESCRIPTION OF THE INVENTION
[0011] In general, the invention may be used to remove a nitrogen
or sulfur compound or other hydrocarbon containing impurity from a
hydrocarbon fraction through use of a hydrocarbon-immiscible
phosphonium ionic liquid.
[0012] The terms "vacuum gas oil", "VGO", "VGO phase" and similar
terms relating to vacuum gas oil as used herein are to be
interpreted broadly to receive not only their ordinary meanings as
used by those skilled in the art of producing and converting such
hydrocarbon fractions, but also in a broad manner to account for
the application of our processes to hydrocarbon fractions
exhibiting VGO-like characteristics. Thus, the terms encompass
straight run VGO as may be produced in a crude fractionation
section of an oil refinery, as well as, VGO product cuts,
fractions, or streams that may be produced, for example, by coker,
deasphalting, and visbreaking processing units, or which may be
produced by blending various hydrocarbons. In addition to the
processing of vacuum gas oils, it is contemplated that the
processing of certain other hydrocarbons would benefit from the
regeneration process of the present invention.
[0013] In general, the hydrocarbon feed has a specific gravity from
about 0.8 to 1.2. The hydrocarbon feed may be a VGO which comprises
petroleum hydrocarbon components boiling in the range of from about
100.degree. to about 720.degree. C. In an embodiment the VGO boils
from about 250.degree. to about 650.degree. C. and has a specific
gravity in the range of from about 0.8 to about 0.95. The nitrogen
content may be determined using ASTM method D4629-02, Trace
Nitrogen in Liquid Petroleum Hydrocarbons by Syringe/Inlet
Oxidative Combustion and Chemiluminescence Detection. The sulfur
content may be determined using ASTM method D5453-00, Ultraviolet
Fluorescence; and the metals content may be determined by
UOP389-09, Trace Metals in Oils by Wet Ashing and ICP-OES. Unless
otherwise noted, the analytical methods used herein such as ASTM
D5453-00 and UOP389-09 are available from ASTM International, 100
Barr Harbor Drive, West Conshohocken, Pa., USA.
[0014] Processes according to the invention remove nitrogen
compounds and other impurities from a hydrocarbon. That is, the
invention removes at least one type of impurity from hydrocarbons.
It is understood that the hydrocarbon will usually comprise a
plurality of nitrogen compounds of different types in various
amounts. Thus, the process removes at least a portion of at least
one type of nitrogen compound from the hydrocarbon. Other compounds
such as sulfur compounds may also be removed from the hydrocarbon.
These compounds are defined as "hydrocarbon impurities" to
differentiate them from the hydrocarbon feed and from the light
hydrocarbons that are used in the regeneration of the ionic
liquids.
[0015] One or more ionic liquids are used to extract one or more
hydrocarbon impurities from the hydrocarbon. Generally, ionic
liquids are non-aqueous, organic salts composed of ions where the
positive ion is charge balanced with negative ion. These materials
have low melting points, often below 100.degree. C., undetectable
vapor pressure and good chemical and thermal stability. The
cationic charge of the salt is localized over hetero atoms, such as
nitrogen, phosphorous, sulfur, arsenic, boron, antimony, and
aluminum, and the anions may be any inorganic, organic, or
organometallic species.
[0016] Ionic liquids suitable for use in the instant invention are
hydrocarbon-immiscible phosphonium ionic liquids. As used herein
the term "hydrocarbon-immiscible phosphonium ionic liquid" means an
ionic liquid having a cation comprising at least one phosphorous
atom and which is capable of forming a separate phase from the
hydrocarbon under operating conditions of the process. Ionic
liquids that are miscible with the hydrocarbon at the process
conditions will be completely soluble with the hydrocarbon;
therefore, no phase separation will be feasible. Thus,
hydrocarbon-immiscible phosphonium ionic liquids may be insoluble
with or partially soluble with the hydrocarbon under operating
conditions. A phosphonium ionic liquid capable of forming a
separate phase from the hydrocarbon under the operating conditions
is considered to be hydrocarbon-immiscible. Ionic liquids according
to the invention may be insoluble, partially soluble, or completely
soluble (miscible) with water.
[0017] In an embodiment, the hydrocarbon-immiscible phosphonium
ionic liquid comprises at least one ionic liquid from at least one
of the following groups of ionic liquids: tetraalkylphosphonium
dialkylphosphates, tetraalkylphosphonium dialkyl phosphinates,
tetraalkylphosphonium phosphates, tetraalkylphosphonium tosylates,
tetraalkylphosphonium sulfates, tetraalkylphosphonium sulfonates,
tetraalkylphosphonium carbonates, tetraalkylphosphonium metalates,
oxometalates, tetraalkylphosphonium mixed metalates,
tetraalkylphosphonium polyoxometalates, and tetraalkylphosphonium
halides. In another embodiment, the hydrocarbon-immiscible
phosphonium ionic liquid comprises at least one of
trihexyl(tetradecyl)phosphonium chloride,
trihexyl(tetradecyl)phosphonium bromide,
tributyl(methyl)phosphonium bromide, tributyl(methyl)phosphonium
chloride, tributyl(hexyl)phosphonium bromide,
tributyl(hexyl)phosphonium chloride, tributyl(octyl)phosphonium
bromide, tributyl(octyl)phosphonium chloride,
tributyl(decyl)phosphonium bromide, tributyl(decyl)phosphonium
chloride, tetrabutylphosphonium bromide, tetrabutylphosphonium
chloride, triisobutyl(methyl)phosphonium tosylate,
tributyl(methyl)phosphonium methylsulfate,
tributyl(ethyl)phosphonium diethylphosphate, and
tetrabutylphosphonium methanesulfonate. In a further embodiment,
the hydrocarbon-immiscible phosphonium ionic liquid is selected
from the group consisting of trihexyl(tetradecyl)phosphonium
chloride, trihexyl(tetradecyl)phosphonium bromide,
tributyl(methyl)phosphonium bromide, tributyl(methyl)phosphonium
chloride, tributyl(hexyl)phosphonium bromide,
tributyl(hexyl)phosphonium chloride, tributyl(octyl)phosphonium
bromide, tributyl(octyl)phosphonium chloride,
tributyl(decyl)phosphonium bromide, tributyl(decyl)phosphonium
chloride, tetrabutylphosphonium bromide, tetrabutylphosphonium
chloride, triisobutyl(methyl)phosphonium tosylate,
tributyl(methyl)phosphonium methylsulfate,
tributyl(ethyl)phosphonium diethylphosphate, tetrabutylphosphonium
methanesulfonate, and combinations thereof. The
hydrocarbon-immiscible phosphonium ionic liquid may be selected
from the group consisting of trihexyl(tetradecyl)phosphonium
halides, tetraalkylphosphonium dialkylphosphates,
tetraalkylphosphonium tosylates, tetraalkylphosphonium sulfonates,
tetraalkylphosphonium halides, and combinations thereof. The
hydrocarbon-immiscible phosphonium ionic liquid may comprise at
least one ionic liquid from at least one of the following groups of
ionic liquids trihexyl(tetradecyl)phosphonium halides,
tetraalkylphosphonium dialkylphosphates, tetraalkylphosphonium
tosylates, tetraalkylphosphonium sulfonates, and
tetraalkylphosphonium halides.
[0018] In an embodiment, the invention is a process for removing
impurities including nitrogen and sulfur compounds from a
hydrocarbon stream comprising a contacting step, a separating step
and a regenerating step. In the contacting step, vacuum gas oil
comprising impurities and a hydrocarbon-immiscible phosphonium
ionic liquid are contacted or mixed. The contacting may facilitate
transfer or extraction of the one or more impurities from the
hydrocarbon to the ionic liquid. Although a hydrocarbon-immiscible
phosphonium ionic liquid that is partially soluble in hydrocarbon
may facilitate transfer of the impurities from the hydrocarbon to
the ionic liquid, partial solubility is not required. Insoluble
hydrocarbon/ionic liquid mixtures may have sufficient interfacial
surface area between the hydrocarbon and ionic liquid to be useful.
In the separation step, the mixture of hydrocarbon and ionic liquid
settles or forms two phases, a hydrocarbon phase and an ionic
liquid phase, which is separated to produce a
hydrocarbon-immiscible phosphonium ionic liquid effluent and a
hydrocarbon effluent. In the regeneration phase, water and a light
hydrocarbon are added to the mixture of hydrocarbon-immiscible
phosphonium ionic liquid effluent. This facilitates the separation
of the hydrocarbon phase (both the hydrocarbon containing
impurities and the added light hydrocarbon from the ionic liquid.
Then the water can be removed from the ionic liquid by the water
being boiled off.
[0019] The process may be conducted in various equipment which are
well known in the art and are suitable for batch or continuous
operation. For example, in a small scale form of the invention,
hydrocarbon and a hydrocarbon-immiscible phosphonium ionic liquid
may be mixed in a beaker, flask, or other vessel, e.g., by
stirring, shaking, use of a mixer, or a magnetic stirrer. The
mixing or agitation is stopped and the mixture forms a hydrocarbon
phase and an ionic liquid phase which can be separated, for
example, by decanting, centrifugation, or use of a pipette to
produce a hydrocarbon effluent having a lower impurities content
relative to the hydrocarbon. The process also produces a
hydrocarbon-immiscible phosphonium ionic liquid effluent comprising
the one or more impurities.
[0020] The contacting and separating steps may be repeated for
example when the impurities content of the hydrocarbon effluent is
to be reduced further to obtain a desired impurities level in the
ultimate hydrocarbon product stream from the process. Each set,
group, or pair of contacting and separating steps may be referred
to as a nitrogen removal step. Thus, the invention encompasses
single and multiple impurities removal steps. A impurities removal
zone may be used to perform a impurities removal step. As used
herein, the term "zone" can refer to one or more equipment items
and/or one or more sub-zones. Equipment items may include, for
example, one or more vessels, heaters, separators, exchangers,
conduits, pumps, compressors, and controllers. Additionally, an
equipment item can further include one or more zones or sub-zones.
The impurities removal process or step may be conducted in a
similar manner and with similar equipment as is used to conduct
other liquid-liquid wash and extraction operations. Suitable
equipment includes, for example, columns with: trays, packing,
rotating discs or plates, and static mixers. Pulse columns and
mixing/settling tanks may also be used.
[0021] The invention can employ an impurities removal or extraction
zone that comprises a multi-stage, counter-current extraction
column wherein hydrocarbon and hydrocarbon-immiscible phosphonium
ionic liquid are contacted and hydrocarbon containing impurities
separated. The hydrocarbon or hydrocarbon feed stream and a lean
ionic liquid stream enter an extraction column and then a
hydrocarbon effluent and a hydrocarbon-immiscible phosphonium ionic
liquid effluent including the impurities are removed from the
hydrocarbon feed.
[0022] Consistent with common terms of art, the ionic liquid
introduced to the nitrogen removal step may be referred to as a
"lean ionic liquid" generally meaning a hydrocarbon-immiscible
phosphonium ionic liquid that is not saturated with one or more
extracted hydrocarbon impurities. Lean ionic liquid may include one
or both of fresh and regenerated ionic liquid and is suitable for
accepting or extracting nitrogen from the hydrocarbon feed.
Likewise, the ionic liquid effluent may be referred to as "rich
ionic liquid", which generally means a hydrocarbon-immiscible
phosphonium ionic liquid effluent produced by an impurities removal
step or process or otherwise including a greater amount of
extracted impurities than the amount of extracted impurities
included in the lean ionic liquid. A rich ionic liquid may require
regeneration or dilution, e.g. with fresh ionic liquid, before
recycling the rich ionic liquid to the same or another nitrogen
removal step of the process.
[0023] Static in-line mixers that are well known in the art may be
used for contacting the hydrocarbon feed stream with the lean ionic
liquid stream. These mixers may include a conduit with fixed
internals such as baffles, fins, and channels that mix the fluid as
it flows through the conduit. In other embodiments, not
illustrated, lean ionic liquid stream may be introduced into the
hydrocarbon feed stream, or the lean ionic liquid stream and
hydrocarbon feed stream may be combined such as through a "Y"
conduit. In another embodiment, the lean ionic liquid stream and
hydrocarbon feed stream are separately introduced into the static
in-line mixer. In other embodiments, the streams may be mixed by
any method well know in the art including stirred tank and blending
operations. The mixture comprising hydrocarbon and ionic liquid is
transferred to a separation zone which may comprise a separation
vessel wherein the two phases are allowed to separate into a rich
ionic liquid phase which is withdrawn from a lower portion of the
separation vessel and the hydrocarbon phase which is withdrawn from
an upper portion of separation vessel via a hydrocarbon effluent
conduit. The separation vessel may comprise a boot, not
illustrated, from which rich ionic liquid is withdrawn.
[0024] The separation vessel may contain a solid media and/or other
coalescing devices which facilitate the phase separation. In other
embodiments the separation zone may comprise multiple vessels which
may be arranged in series, parallel, or a combination thereof. The
separation vessels may be of any shape and configuration to
facilitate the separation, collection, and removal of the two
phases. In a further embodiment, the nitrogen removal zone may
include a single vessel wherein the lean ionic liquid stream and
hydrocarbon feed stream are mixed, then remain in the vessel to
settle into the hydrocarbon effluent and rich ionic liquid phases.
In an embodiment the process comprises at least two impurities
removal steps. For example, the hydrocarbon effluent from one
impurities removal step may be passed directly as the hydrocarbon
feed to a second impurities removal step. In another embodiment,
the hydrocarbon effluent from one nitrogen removal step may be
treated or processed before being introduced as the hydrocarbon
feed to the second impurities removal step. There is no requirement
that each impurities removal zone comprises the same type of
equipment. Different equipment and conditions may be used in
different nitrogen removal zones.
[0025] The impurities removal step may be conducted under nitrogen
removal conditions including temperatures and pressures sufficient
to keep the hydrocarbon-immiscible phosphonium ionic liquid and
hydrocarbon feeds and effluents as liquids. For example, the
impurities removal step temperature may range between about
10.degree. C. and less than the decomposition temperature of the
phosphonium ionic liquid; and the pressure may range between about
atmospheric pressure and about 700 kPa(g). When the
hydrocarbon-immiscible ionic liquid comprises more than one ionic
liquid component, the decomposition temperature of the ionic liquid
is the lowest temperature at which any of the ionic liquid
components decompose. The nitrogen removal step may be conducted at
a uniform temperature and pressure or the contacting and separating
steps of the nitrogen removal step may be operated at different
temperatures and/or pressures. In an embodiment, the contacting
step is conducted at a first temperature, and the separating step
is conducted at a temperature at least 5.degree. C. lower than the
first temperature. In a non limiting example, the first temperature
is about 80.degree. C. Such temperature differences may facilitate
separation of the hydrocarbon and ionic liquid phases.
[0026] The above and other nitrogen removal step conditions such as
the contacting or mixing time, the separation or settling time, and
the ratio of hydrocarbon feed to hydrocarbon-immiscible phosphonium
ionic liquid (lean ionic liquid) may vary greatly based, for
example, on the specific ionic liquid or liquids employed, the
nature of the hydrocarbon feed (straight run or previously
processed), the impurities content of the hydrocarbon feed, the
degree of impurities removal required, the number of impurities
removal steps employed, and the specific equipment used. In general
it is expected that contacting time may range from less than one
minute to about two hours; settling time may range from about one
minute to about eight hours; and the weight ratio of hydrocarbon
feed to lean ionic liquid introduced to the impurities removal step
may range from 1:10,000 to 10,000:1. In an embodiment, the weight
ratio of hydrocarbon feed to lean ionic liquid may range from about
1:1,000 to about 1,000:1; and the weight ratio of hydrocarbon feed
to lean ionic liquid may range from about 1:100 to about 100:1. In
an embodiment the weight of hydrocarbon feed is greater than the
weight of ionic liquid introduced to the nitrogen removal step.
[0027] In an embodiment, a single impurities removal step reduces
the impurities content of the hydrocarbon by more than about 40
wt-%. In another embodiment, more than about 50% of the impurities
by weight is extracted or removed from the hydrocarbon feed in a
single impurities removal step; and more than about 60% of the
nitrogen by weight may be extracted or removed from the hydrocarbon
feed in a single impurities removal step. As discussed herein the
invention encompasses multiple impurities removal steps to provide
the desired amount of impurities removal. The degree of phase
separation between the hydrocarbon and ionic liquid phases is
another factor to consider as it affects recovery of the ionic
liquid and hydrocarbon. The degree of impurities removed and the
recovery of the hydrocarbon and ionic liquids may be affected
differently by the nature of the hydrocarbon feed, the specific
ionic liquid or liquids, the equipment, and the impurities removal
conditions such as those discussed above.
[0028] The amount of water present in the
hydrocarbon/hydrocarbon-immiscible phosphonium ionic liquid mixture
during the impurities removal step may also affect the amount of
hydrocarbon removed and/or the degree of phase separation, i.e.,
recovery of the hydrocarbon and ionic liquid. In an embodiment, the
hydrocarbon/hydrocarbon-immiscible phosphonium ionic liquid mixture
has a water content of less than about 10% relative to the weight
of the ionic liquid. In another embodiment, the water content of
the hydrocarbon/hydrocarbon-immiscible phosphonium ionic liquid
mixture is less than about 5% relative to the weight of the ionic
liquid; and the water content of the
hydrocarbon/hydrocarbon-immiscible phosphonium ionic liquid mixture
may be less than about 2% relative to the weight of the ionic
liquid. In a further embodiment, the
hydrocarbon/hydrocarbon-immiscible phosphonium ionic liquid mixture
is water free, i.e., the mixture does not contain water.
[0029] After the ionic liquid contacts the hydrocarbon stream to
remove the impurities, a hydrocarbon washing step is used to
recover ionic liquid that is entrained or otherwise remains in the
hydrocarbon effluent stream by using water to wash or extract the
ionic liquid from the hydrocarbon effluent. Various hydrocarbon
washing step equipment and conditions such as temperature,
pressure, times, and solvent to feed ratio may be the same as or
different from the nitrogen removal zone equipment and conditions.
In general, the hydrocarbon washing step conditions will fall
within the same ranges as given above for the impurities removal
step conditions. A portion or all of the washed hydrocarbon stream
may be passed to a hydrocarbon conversion zone.
[0030] An ionic liquid regeneration step is used to regenerate the
ionic liquid by removing the hydrocarbon impurities from the ionic
liquid, i.e. reducing the nitrogen content of the rich ionic
liquid. In an embodiment, a portion or all of a
hydrocarbon-immiscible phosphonium ionic liquid effluent stream (as
feed) comprising the hydrocarbon impurities and a regeneration
solvent stream are introduced to an ionic liquid regeneration zone.
The hydrocarbon-immiscible phosphonium ionic liquid effluent and
regeneration solvent streams are mixed and separated to produce an
extract stream comprising the hydrocarbon impurities, and a
regenerated ionic liquid stream. The ionic liquid regeneration step
may be conducted in a similar manner and with similar equipment as
used to conduct other liquid-liquid wash and extraction operations
as discussed above. Various ionic liquid regeneration step
conditions such as temperature, pressure, times, and solvent to
feed may be the same as or different from the nitrogen removal
conditions. In general, the ionic liquid regeneration step
conditions will fall within the same ranges as given above for the
nitrogen removal step conditions.
[0031] In an embodiment, the regeneration solvent stream comprises
a mixture of water and a light hydrocarbon which is immiscible with
the phosphonium ionic liquid and water. In an embodiment, the light
hydrocarbon has a lower average boiling point than the hydrocarbon
feed. The light hydrocarbon fraction may consist of a single
hydrocarbon compound or may comprise a mixture of hydrocarbons. In
an embodiment, the light hydrocarbon fraction comprises at least
one of a naphtha, gasoline, diesel, kerosene, light cycle oil
(LCO), toluene, benzene and light coker gas oil (LCGO) hydrocarbon
fraction. In an embodiment, this light hydrocarbon fraction may be
the hydrocarbon feed itself or it may be any other hydrocarbon with
a specific gravity lower than that of the hydrocarbon feed. The
light hydrocarbon fraction may comprise straight run fractions
and/or products from conversion processes such as hydrocracking,
hydrotreating, fluid catalytic cracking (FCC), reforming, coking,
and visbreaking In this embodiment, the extract stream comprises
the light hydrocarbon fraction of the regeneration solvent and the
hydrocarbon impurities. A portion or the entire regenerated
hydrocarbon-immiscible phosphonium ionic liquid stream may be
recycled to the impurities removal step via a conduit not shown
consistent with other operating conditions of the process. For
example, a constraint on the water content of the
hydrocarbon-immiscible phosphonium ionic liquid stream or the ionic
liquid/hydrocarbon mixture in the impurities removal zone may be
met by controlling the proportion and water content of fresh and
recycled ionic liquid streams. In an embodiment, the water fraction
of the regeneration solvent stream is added to the
hydrocarbon-immiscible phosphonium ionic liquid stream, and the
light hydrocarbon fraction is added to achieve countercurrent flow
to the hydrocarbon-immiscible phosphonium ionic liquid stream.
[0032] The ionic liquid drying step may be employed to reduce the
water content of one or more of the streams comprising ionic liquid
to control the water content of the nitrogen removal step as
described above. In the embodiment of the invention, a portion or
all of regenerated hydrocarbon-immiscible phosphonium ionic liquid
stream is introduced to a drying zone. Although not shown, other
streams comprising ionic liquid such as the fresh ionic liquid
stream, hydrocarbon-immiscible phosphonium ionic liquid effluent
stream, and spent water stream, may also be dried in any
combination in the drying zone. To dry the ionic liquid stream or
streams, water may be removed by one or more various well known
methods including distillation, flash distillation, multistage
evaporation, and using a dry inert gas to strip water. Generally,
the drying temperature may range from about 100.degree. C. to less
than the decomposition temperature of the ionic liquid, usually
less than about 300.degree. C. The pressure may range from about 35
to about 350 kPa. The drying step produces a dried
hydrocarbon-immiscible phosphonium ionic liquid stream and a drying
zone water effluent stream. Although not illustrated, a portion or
all of dried hydrocarbon-immiscible phosphonium ionic liquid stream
may be recycled or passed to provide all or a portion of the
hydrocarbon-immiscible phosphonium ionic liquid introduced to
impurities removal zone. A portion or all of drying zone water
effluent stream may be recycled or passed to provide all or a
portion of the water introduced into hydrocarbon washing zone
and/or ionic liquid regeneration zone.
[0033] The FIGURE shows a simplified flow scheme in which a
hydrocarbon feed stream 2 is sent to an extraction unit 6
containing ionic liquid which is shown in line 4 entering the
extraction unit 6. The ionic liquid removes impurities with the
clean hydrocarbon exiting in line 8 and the ionic liquid containing
the impurities is sent in line 10 to regenerator unit 14. Water
enters regenerator 14 through line 12 and a light hydrocarbon such
as naphtha, kerosene or benzene enters regenerator 14 through line
28. A stream comprising the light hydrocarbon and the impurities is
shown in line 24 going to an evaporator 26 in which the hydrocarbon
is vaporized and is sent in line 28 to return to the regenerator
14. The impurities exit evaporator 26 through line 30. The ionic
liquid and water from regenerator 14 are sent through line 16 to a
second evaporator 18 with the ionic liquid flowing out the bottom
of the unit in line 20 to be recycled to the ionic liquid in line
4. The water is (not shown) being evaporated from evaporator
18.
[0034] Unless otherwise stated, the exact connection point of
various inlet and effluent streams within the zones is not
essential to the invention. For example, it is well known in the
art that a stream to a distillation zone may be sent directly to
the column, or the stream may first be sent to other equipment
within the zone such as heat exchangers, to adjust temperature,
and/or pumps to adjust the pressure. Likewise, streams entering and
leaving impurities removal, washing, and regeneration zones may
pass through ancillary equipment such as heat exchanges within the
zones. Streams, including recycle streams, introduced to washing or
extraction zones may be introduced individually or combined prior
to or within such zones.
[0035] The invention encompasses a variety of flow scheme
embodiments including optional destinations of streams, splitting
streams to send the same composition, i.e. aliquot portions, to
more than one destination, and recycling various streams within the
process. Examples include: various streams comprising ionic liquid
and water may be dried and/or passed to other zones to provide all
or a portion of the water and/or ionic liquid required by the
destination zone. The various process steps may be operated
continuously and/or intermittently as needed for a given embodiment
e.g. based on the quantities and properties of the streams to be
processed in such steps. As discussed above the invention
encompasses multiple nitrogen removal steps, which may be performed
in parallel, sequentially, or a combination thereof. Multiple
nitrogen removal steps may be performed within the same nitrogen
removal zone and/or multiple nitrogen removal zones may be employed
with or without intervening washing, regeneration and/or drying
zones.
[0036] The following examples are illustrative of the present
invention in showing the advantages to the use of naphtha or
kerosene as the light hydrocarbon to separate the impurities from
the water/ionic liquid mixture.
COMPARATIVE EXAMPLE
[0037] A sample of triisobutylmethylphosphonium tosylate (ionic
liquid) with a specific gravity of 1.05 and vacuum gas oil (VGO)
with a specific gravity of 0.9271 were combined in a beaker at
ratio of 10:1 VGO:ionic liquid. The beaker was placed onto a heated
stir plate and stirred at 80.degree. C. for 30 minutes. After 30
minutes, the stirring was stopped and the ionic liquid mixture was
allowed to settle for 30 minutes. A pipette was used to draw off
the extracted VGO from the ionic liquid. The specific gravity of
the extracted VGO was 0.909. The resulting
triisobutylmethylphosphonium tosylate and extract from the VGO had
a specific gravity of 1.033. Water was added to mixture of
triisobutylmethylphosphonium tosylate and extract at a ratio of 1:1
mixture:water. The triisobutylmethylphosphonium tosylate
preferentially combined with the water and the extract was freed
from the mixture. The combined water and ionic liquid had a
specific gravity of 1.017 and the extract had a specific gravity of
1.016. Because the specific gravities of the two phases were very
similar a clean separation did not occur.
EXAMPLE 1
[0038] A sample of triisobutylmethylphosphonium tosylate with a
specific gravity of 1.05 and vacuum gas oil (VGO) with a specific
gravity of 0.9271 were combined in a beaker at ratio of 10:1
VGO:ionic liquid. The beaker was placed onto a heated stir plate
and stirred at 80.degree. C. for 30 minutes. After 30 minutes, the
stirring was stopped and the ionic liquid mixture was allowed to
settle for 30 minutes. A pipette was used to draw off the extracted
VGO from the ionic liquid. The specific gravity of the extracted
VGO was 0.909. The resulting triisobutylmethylphosphonium tosylate
and extract from the VGO had a specific gravity of 1.033. Water and
naphtha were added to a mixture of triisobutylmethylphosphonium
tosylate and extract at a ratio of 1:1:0.2 mixture:water:naphtha.
The naphtha had a specific gravity of 0.6637. The
triisobutylmethylphosphonium tosylate preferentially combined with
the water and the naphtha combined with the extract. The density of
the naphtha combined with the extract was less than 1.017, the
specific gravity of the ionic liquid plus water, as a result, the
extract floated.
EXAMPLE 2
[0039] A sample of tributylethylphosphonium diethylphosphate with a
specific gravity of 0.996 and vacuum gas oil (VGO) with a specific
gravity of 0.9271 were combined in a beaker at ratio of 10:1
VGO:ionic liquid. The beaker was placed onto a heated stir plate
and stirred at 80.degree. C. for 30 minutes. After 30 minutes, the
stirring was stopped and the ionic liquid mixture was allowed to
settle for 30 minutes. A pipette was used to draw off the extracted
VGO from the ionic liquid. The specific gravity of the extracted
VGO was 0.9236. Water and naphtha were added to mixture of
tributylethylphosphonium diethylphosphate and extract at a ratio of
1:1:0.2 mixture:water:naphtha. The naphtha had a specific gravity
of 0.6637. The tributylethylphosphonium diethylphosphate
preferentially combined with the water and the naphtha combined
with the extract. The density of the naphtha combined with the
extract was less than 0.98, the specific gravity of the ionic
liquid plus water, as a result, the extract floated.
EXAMPLE 3
[0040] A sample of triisobutylmethylphosphonium tosylate with a
specific gravity of 1.05 and vacuum gas oil (VGO) with a specific
gravity of 0.9271 were combined in a beaker at ratio of 10:1
VGO:ionic liquid. The beaker was placed onto a heated stir plate
and stirred at 80.degree. C. for 30 minutes. After 30 minutes, the
stirring was stopped and the ionic liquid mixture was allowed to
settle for 30 minutes. A pipette was used to draw off the extracted
VGO from the ionic liquid. The specific gravity of the extracted
VGO was 0.924. The resulting triisobutylmethylphosphonium tosylate
and extract from the VGO had a specific gravity of 1.033. Water and
kerosene were added to the mixture of triisobutylmethylphosphonium
tosylate and extract at a ratio of 1:1:0.2 mixture:water:kerosene.
The kerosene had a specific gravity of 0.8112 The
triisobutylmethylphosphonium tosylate preferentially combined with
the water and the kerosene combined with the extract. The density
of the kerosene combined with the extract was less than 1.017, the
specific gravity of the ionic liquid plus water, as a result, the
extract floated.
* * * * *