U.S. patent application number 14/039882 was filed with the patent office on 2014-01-23 for process to remove dissolved alcl3 from ionic liquid.
This patent application is currently assigned to CHEVRON U.S.A. INC.. The applicant listed for this patent is Moinuddin Ahmed, Bong-Kyu Chang, Sara Lindsay, Huping Luo, Krishniah Parimi. Invention is credited to Moinuddin Ahmed, Bong-Kyu Chang, Sara Lindsay, Huping Luo, Krishniah Parimi.
Application Number | 20140024874 14/039882 |
Document ID | / |
Family ID | 42196933 |
Filed Date | 2014-01-23 |
United States Patent
Application |
20140024874 |
Kind Code |
A1 |
Ahmed; Moinuddin ; et
al. |
January 23, 2014 |
PROCESS TO REMOVE DISSOLVED AlCl3 FROM IONIC LIQUID
Abstract
Disclosed herein are processes in which precipitation permits
removal of metal halides (e.g. AlCl.sub.3) from ionic liquids.
After precipitation, the precipitated metal halides can be
physically separated from the bulk ionic liquid. More effective
precipitation can be achieved through cooling or the combination of
cooling and the provision of metal halide seed crystals. The ionic
liquids can be regenerated ionic liquid catalysts, which contain
excess metal halides after regeneration. Upon removal of the excess
metal halides, they can be reused in processes using ionic liquid
catalysts, such as alkylation processes.
Inventors: |
Ahmed; Moinuddin; (San
Ramon, CA) ; Luo; Huping; (San Ramon, CA) ;
Parimi; Krishniah; (San Ramon, CA) ; Chang;
Bong-Kyu; (San Ramon, CA) ; Lindsay; Sara;
(San Ramon, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ahmed; Moinuddin
Luo; Huping
Parimi; Krishniah
Chang; Bong-Kyu
Lindsay; Sara |
San Ramon
San Ramon
San Ramon
San Ramon
San Ramon |
CA
CA
CA
CA
CA |
US
US
US
US
US |
|
|
Assignee: |
CHEVRON U.S.A. INC.
San Ramon
CA
|
Family ID: |
42196933 |
Appl. No.: |
14/039882 |
Filed: |
September 27, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13830750 |
Mar 14, 2013 |
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14039882 |
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|
12324570 |
Nov 26, 2008 |
8541638 |
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13830750 |
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Current U.S.
Class: |
585/712 |
Current CPC
Class: |
Y02P 20/584 20151101;
C07C 2/60 20130101; C07C 2527/126 20130101; B01J 31/40 20130101;
B01J 31/0277 20130101; C07C 2/58 20130101; B01J 31/0284 20130101;
B01J 31/4061 20130101 |
Class at
Publication: |
585/712 |
International
Class: |
C07C 2/58 20060101
C07C002/58 |
Claims
1. An alkylation process, comprising: a) conducting an alkylation
reaction with an ionic liquid catalyst to provide a product and a
spent ionic liquid catalyst; b) reacting the spent ionic liquid
catalyst with aluminum to provide a regenerated ionic liquid
catalyst and excess dissolved AlCl.sub.3; c) precipitating the
excess dissolved AlCl.sub.3 from the regenerated ionic liquid
catalyst to provide precipitated excess AlCl.sub.3; d) removing the
precipitated excess AlCl.sub.3 from the regenerated ionic liquid
catalyst; and e) recycling the regenerated ionic liquid catalyst to
reaction step a).
2. The process according to claim 1, further comprising isolating
the product from the alkylation reaction.
3. The process according to claim 1, further comprising removing
the precipitated excess AlCl.sub.3 by filtration.
4. The process according to claim 1, further comprising removing
the precipitated excess AlCl.sub.3 by decantation.
5. The process according to claim 1, wherein the mixture is cooled
to a temperature less than about 50.degree. C. to precipitate the
excess dissolved AlCl.sub.3.
6. The process according to claim 1, wherein the mixture is cooled
to about room temperature or to less than about room temperature to
precipitate the excess dissolved AlCl.sub.3.
7. The process of claim 1, wherein the ionic liquid catalyst is
n-butyl pyridinium chloroaluminate.
8. An alkylation process, comprising: a) conducting an alkylation
reaction with an ionic liquid catalyst to provide a product and a
spent ionic liquid catalyst; b) reacting the spent ionic liquid
catalyst with aluminum to provide a regenerated ionic liquid
catalyst and excess dissolved AlCl.sub.3; c) feeding the
regenerated ionic liquid catalyst and dissolved AlCl.sub.3 to a
vessel and providing metal halide seed crystals to provide a
mixture comprising regenerated ionic liquid catalyst, dissolved
AlCl.sub.3, and metal halide seed crystals; d) cooling the mixture
in the vessel to provide precipitated AlCl.sub.3; e) removing the
precipitated AlCl.sub.3 from the vessel, and f) recycling the
regenerated ionic liquid catalyst to reaction step a).
9. The process according to claim 8, further comprising removing
the precipitated excess AlCl.sub.3 by filtration.
10. The process according to claim 8, further comprising removing
the precipitated excess AlCl.sub.3 by decantation.
11. The process according to claim 8, wherein the mixture is cooled
to a temperature less than about 50.degree. C. to precipitate the
excess dissolved AlCl.sub.3.
12. The process according to claim 8, wherein the mixture is cooled
to about room temperature or to less than about room temperature to
precipitate the excess dissolved AlCl.sub.3.
13. The process of claim 8, wherein the ionic liquid catalyst is
n-butyl pyridinium chloroaluminate.
14. The process according to claim 8, further comprising isolating
the product from the alkylation reaction.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present invention is a divisional of U.S. patent
application Ser. No. 13/830,750 filed Mar. 14, 2013, which is a
divisional of U.S. patent application Ser. No. 12/324,570 filed
Nov. 26, 2008, the contents of which are hereby incorporated by
reference in their entirety.
FIELD OF ART
[0002] The present disclosure relates to a process for removing
metal halides from an ionic liquid. In particular, the process
involves precipitating metal halides out of a mixture comprising
the ionic liquid and metal halides. More particularly, the present
disclosure relates to removing metal halides (e.g. AlCl.sub.3) from
a regenerated ionic liquid catalyst involving precipitating metal
halides out of a mixture comprising the regenerated ionic liquid
catalyst and metal halides.
BACKGROUND
[0003] An alkylation process, which is disclosed in U.S. Patent
Application Publication 2006/0131209 ("the '209 publication"),
involves contacting isoparaffins, preferably isopentane, with
olefins, preferably ethylene, in the presence of an ionic liquid
catalyst to produce gasoline blending components. The contents of
the '209 publication are incorporated by reference herein in its
entirety.
[0004] An ionic liquid catalyst distinguishes this novel alkylation
process from conventional processes that convert light paraffins
and light olefins to more lucrative products such as the alkylation
of isoparaffins with olefins and the polymerization of olefins. For
example, two of the more extensively used processes to alkylate
isobutane with C.sub.3-C.sub.5 olefins to make gasoline cuts with
high octane numbers use sulfuric acid (H.sub.2SO.sub.4) and
hydrofluoric acid (HF) catalysts.
[0005] Ionic liquid catalysts specifically useful in the alkylation
process described in the '209 publication are disclosed in U.S.
Patent Application Publication 2006/0135839 ("the '839
publication"), which is also incorporated by reference in its
entirety herein. Such catalysts include a chloroaluminate ionic
liquid catalyst comprising a hydrocarbyl substituted pyridinium
halide and aluminum trichloride or a hydrocarbyl substituted
imidazolium halide and aluminum trichloride. Such catalysts further
include chloroaluminate ionic liquid catalysts comprising an alkyl
substituted pyridinium halide and aluminum trichloride or an alkyl
substituted imidazolium halide and aluminum trichloride. Preferred
chloroaluminate ionic liquid catalysts include
1-butyl-4-methyl-pyridinium chloroaluminate (BMP),
1-butyl-pyridinium chloroaluminate (BP),
1-butyl-3-methyl-imidazolium chloroaluminate (BMIM) and
1-H-pyridinium chloroaluminate (HP).
[0006] However, ionic liquid catalysts have unique properties
making it necessary to further develop and modify the ionic liquid
catalyzed alkylation process in order to achieve superior gasoline
blending component products, improved process operability and
reliability, reduced operating costs, etc. For example, as a result
of use, ionic liquid catalysts become deactivated, i.e. lose
activity, and may eventually need to be replaced.
[0007] Alkylation processes utilizing an ionic liquid catalyst form
by-products known as conjunct polymers. These conjunct polymers can
deactivate the ionic liquid catalyst by forming complexes with the
ionic liquid catalyst. Conjunct polymers are highly unsaturated
molecules and may complex the Lewis acid portion of the ionic
liquid catalyst via their double bonds network system. As the
aluminum trichloride becomes complexed with conjunct polymers, the
activity of the ionic liquid becomes impaired or at least
compromised. Conjunct polymers may also become chlorinated and
through their chloro groups may interact with aluminum trichloride
and therefore reduce the overall activity of the catalyst or lessen
its effectiveness as a catalyst for the intended purpose such as
alkylation. Deactivation of the ionic liquid catalyst by conjunct
polymers is not only problematic for the alkylation chemistry, but
also weighs in heavily on the economics of using ionic liquids
because they are expensive catalytic systems and their frequent
replacement will be costly. Therefore, commercial exploitation of
ionic liquid catalysts during alkylation is impossible unless they
are efficiently regenerated and recycled.
[0008] U.S. patent application Ser. No. 12/003,578 ("the '578
application) is directed to a process for regenerating an ionic
liquid catalyst which has been deactivated by conjunct polymers.
The process comprises the steps of (a) providing an ionic liquid
catalyst, wherein at least a portion of the ionic liquid catalyst
is bound to conjunct polymers; (b) reacting the ionic liquid
catalyst with aluminum metal to free the conjunct polymers from the
ionic liquid catalyst in a stirred reactor or a fixed bed reactor;
and (c) separating the freed conjunct polymers from the catalyst
phase by solvent extraction in a stirred or packed extraction
column. The contents of the '578 application are incorporated by
reference herein in their entirety.
[0009] In order to provide regenerated ionic liquid catalyst, in
the process of the '578 application, spent ionic liquid catalyst
reacts with aluminum metal. If the spent ionic liquid catalyst is a
chloroaluminate ionic liquid catalyst, such as catalysts disclosed
in the '839 publication, it produces aluminum trichloride
(AlCl.sub.3) as a byproduct. The AlCl.sub.3 byproduct can remain
dissolved in the regenerated catalyst. Accordingly, it is necessary
to separate the regenerated catalyst and the AlCl.sub.3 byproduct
so that the regenerated catalyst can be recycled to the alkylation
step.
[0010] Therefore, there is a need for an effective and efficient
process for removing metal halides from an ionic liquid catalyst,
and, in particular, a regenerated ionic liquid catalyst. In
general, the process should be simple and efficient enough to be
used to separate any metal halide from an ionic liquid.
SUMMARY
[0011] A process for removing metal halides from an ionic liquid is
described herein. In one embodiment, the process for removing metal
halides from an ionic liquid comprises causing the metal halides to
precipitate out of the ionic liquid. Enhanced precipitation can be
caused by cooling. Cooling can also cause precipitation, which can
provide metal halide seed crystals.
[0012] In another embodiment, a process for removing metal halides
from an ionic liquid comprises: a) feeding the ionic liquid
comprising metal halides to a vessel and providing metal halide
seed crystals to provide a mixture comprising ionic liquid, metal
halides, and metal halide seed crystals; b) cooling the mixture in
the vessel to provide precipitated metal halides; and c) removing
the precipitated metal halides from the vessel.
[0013] The ionic liquid may be an ionic liquid catalyst, which,
after use, may be regenerated in a manner that produces excess
metal halides (e.g. AlCl.sub.3) in the regenerated ionic liquid
catalyst. Therefore, a process for regenerating an ionic liquid
catalyst is also disclosed herein. The process includes: a)
reacting an ionic liquid catalyst with aluminum to provide a
regenerated ionic liquid catalyst containing excess AlCl.sub.3; b)
precipitating the excess AlCl.sub.3 from the regenerated ionic
liquid catalyst to provide precipitated excess AlCl.sub.3; and c)
removing the precipitated excess AlCl.sub.3 from the regenerated
ionic liquid catalyst.
[0014] The ionic liquid catalyst and regenerated ionic liquid
catalyst can be utilized in an alkylation reaction. Therefore, an
alkylation process is further disclosed herein. The alkylation
process includes: a) conducting an alkylation reaction with an
ionic liquid catalyst to provide a product and a spent ionic liquid
catalyst; b) reacting the spent ionic liquid catalyst with aluminum
to provide a regenerated ionic liquid catalyst and excess
AlCl.sub.3; c) precipitating the excess AlCl.sub.3 from the
regenerated ionic liquid catalyst to provide precipitated excess
AlCl.sub.3; d) removing the precipitated excess AlCl.sub.3 from the
regenerated ionic liquid catalyst; and e) recycling the regenerated
ionic liquid catalyst to reaction step a).
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic illustration of an embodiment of the
process whereby metal halides are removed from an ionic liquid in a
crystallization vessel.
[0016] FIG. 2 depicts particle size distribution of AlCl.sub.3
crystals precipitated in Example 5.
DETAILED DESCRIPTION
Process for Removing Metal Halides from Ionic Liquid
[0017] In one aspect, the present process is directed to removing
metal halides from an ionic liquid by precipitation. Accordingly,
the present process involves causing the metal halides to
precipitate out of the ionic liquid.
[0018] In one embodiment, the process involves cooling a mixture
comprising the metal halides and ionic liquid to precipitate the
metal halides out of the ionic liquid. Cooling facilitates
precipitation of the metal halides from the mixture. Upon cooling,
the metal halides generally first form metal halide seed crystals,
which are extremely small, solid particles of the metal halide. The
reduced temperature then facilitates precipitation of additional
metal halide onto the metal halide seed crystals, causing the metal
halide seed crystals to grow into larger, solid particles of
precipitated metal halides. Accordingly, the process can further
involve cooling a mixture comprising metal halides and ionic liquid
containing metal halide seed crystals.
[0019] It has been discovered that cooling and its associated
formation of seed crystals is particularly advantageous. As
discussed above, cooling facilitates precipitation. Cooling may
even enhance precipitation rate. Seed crystals further facilitate
precipitation and may increase the precipitation rate.
[0020] As explained above, the metal halide seed crystals form
naturally during cooling of the mixture. However, additional metal
halide seed crystals may be added to the mixture prior to cooling
or during cooling. Adding seed crystals further enhances
precipitation and results in larger particles which are easier to
separate.
[0021] The temperature to which the metal halide/ionic liquid
mixture or metal halide/ionic liquid/metal halide seed crystal
mixture is cooled can vary. However, the temperature should be
lower than the saturation temperature for the particular metal
halide to be removed from the ionic liquid. In one embodiment, the
mixture can be cooled to a temperature less than about 50.degree.
C. In another embodiment, the mixture can be cooled to about room
temperature. In yet another embodiment, the mixture can be cooled
to a temperature less than about room temperature.
[0022] After the precipitated metal halides form, they can be
physically separated from the mixture and/or ionic liquid. Any
known separation technique can be utilized depending upon time
constraints, desired throughput, etc. For example, the precipitated
metal halides can be separated by decantation or filtration.
Filtration allows for faster separation of the precipitated metal
halides, because filtration does not require the precipitated metal
halides to settle out of the bulk liquid like decantation. As such,
one embodiment of the present process separates the precipitated
metal halides from the bulk liquid by filtration.
[0023] The process can be either a batch process or a continuous
process. Metal halide seed crystals are generally present in a
continuous process.
Ionic Liquids
[0024] As used herein, the term "ionic liquids" refers to liquids
that are composed entirely of ions as a combination of cations and
anions. The term "ionic liquids" includes low-temperature ionic
liquids, which are generally organic salts with melting points
under 100.degree. C. and often even lower than room
temperature.
[0025] Ionic liquids may be suitable, for example, for use as a
catalyst and as a solvent in alkylation and polymerization
reactions as well as in dimerization, oligomerization, acetylation,
olefin metathesis, and copolymerization reactions. The present
embodiments are useful with regard to any ionic liquid
catalyst.
[0026] One class of ionic liquids is fused salt compositions, which
are molten at low temperature and are useful as catalysts,
solvents, and electrolytes. Such compositions are mixtures of
components, which are liquid at temperatures below the individual
melting points of the components.
[0027] The most common ionic liquids are those prepared from
organic-based cations and inorganic or organic anions. The most
common organic cations are ammonium cations, but phosphonium and
sulphonium cations are also frequently used. Ionic liquids of
pyridinium and imidazolium are perhaps the most commonly used
cations. Anions include, but are not limited to, BF.sub.4--,
PF.sub.6--, haloaluminates such as Al.sub.2Cl.sub.7-- and
Al.sub.2Br.sub.7--, [(CF.sub.3SO.sub.2).sub.2N].sup.-, alkyl
sulphates (RSO.sub.3.sup.-), carboxylates (RCO.sub.2.sup.-) and
many others. The most catalytically interesting ionic liquids for
acid catalysis are those derived from ammonium halides and Lewis
acids (such as AlCl.sub.3, TiCl.sub.4, SnCl.sub.4, FeCl.sub.3,
etc.). Chloroaluminate ionic liquids are perhaps the most commonly
used ionic liquid catalyst systems for acid-catalyzed
reactions.
[0028] Examples of such low temperature ionic liquids or molten
fused salts are the chloroaluminate salts. Alkyl imidazolium or
pyridinium chlorides, for example, can be mixed with aluminum
trichloride (AlCl.sub.3) to form the fused chloroaluminate
salts.
[0029] The ionic liquid from which the metal halides are subject to
removal can be any ionic liquid. The metal halide removal process
as disclosed herein is not limited to regenerated ionic liquid
catalysts or ionic liquid catalysts undergoing regeneration. For
example, the metal halide removal process may be used to remove
metal halide contamination from an ionic liquid.
Process for Regenerating an Ionic Liquid Catalyst
[0030] The present process is particularly useful when the ionic
liquid is a regenerated ionic liquid catalyst. The present process
works most effectively when the ionic liquid catalyst is fully
regenerated, meaning that the ionic liquid catalyst is
substantially free from conjunct polymers. The presence of conjunct
polymers generally increases the solubility of metal halides (e.g.
AlCl.sub.3) in ionic liquid thereby making it difficult to
precipitate out metal halides (e.g. AlCl.sub.3). Accordingly, the
present process is not nearly as effective when the ionic liquid
catalyst is only partially regenerated, meaning that the ionic
liquid catalyst still includes conjunct polymers such that it is
not substantially free from conjunct polymers.
[0031] A used or spent ionic liquid catalyst can be regenerated by
contacting the used catalyst with a regeneration metal in the
presence or absence of hydrogen. The metal selected for
regeneration is based on the composition of the ionic liquid
catalyst. The metal should be selected carefully to prevent the
contamination of the catalyst with unwanted metal complexes or
intermediates that may form and remain in the ionic liquid catalyst
phase. The regeneration metal can be selected from Groups III-A,
II-B or I-B. For example, the regeneration metal can be B, Al, Ga,
In, Tl, Zn, Cd, Cu, Ag, or Au. The regeneration metal may be used
in any form, alone, in combination or as alloys.
[0032] Regenerating an ionic liquid catalyst in this manner can
form excess, dissolved metal halide in the regenerated ionic liquid
catalyst. It is then necessary to remove this excess, dissolved
metal halide from the regenerated catalyst before it can be
recycled to the process utilizing the ionic liquid catalyst and in
need of regenerated catalyst. Moreover, the metal halide must be
removed to prevent it from accumulating in the regeneration zone
and other parts of the regeneration unit and causing plugging
problems.
[0033] For example, deactivated, or at least partially deactivated,
chloroaluminate ionic liquid catalyst can be reacted with aluminum
metal, in the presence or absence of hydrogen, to regenerate the
chloroaluminate ionic liquid catalyst. However, the reaction with
aluminum metal can form excess, dissolved AlCl.sub.3 in the
regenerated chloroaluminate ionic liquid catalyst. It is necessary
to remove this excess, dissolved AlCl.sub.3 prior to recycling the
regenerated chloroaluminate ionic liquid catalyst to, for example,
an alkylation reaction.
[0034] Accordingly, the present disclosure further provides a
process for regenerating an ionic liquid catalyst. Such
regeneration process includes the following steps: a) reacting an
ionic liquid catalyst with aluminum to provide a regenerated ionic
liquid catalyst containing excess AlCl.sub.3; b) precipitating the
excess AlCl.sub.3 from the regenerated ionic liquid catalyst to
provide precipitated excess AlCl.sub.3; and c) removing the
precipitated excess AlCl.sub.3 from the regenerated ionic liquid
catalyst.
[0035] As used herein, the term "excess AlCl.sub.3" refers to the
amount of AlCl.sub.3 produced during catalyst regeneration that is
beyond its solubility limit in the ionic liquid catalyst at a
particular temperature such that it may precipitate out during the
regeneration process.
[0036] As described above, the precipitating step can be
accomplished through cooling. More specifically, the precipitating
step can involve cooling the regenerated ionic liquid catalyst to
precipitate excess AlCl.sub.3 from the regenerated ionic liquid
catalyst. This cooling step generally provides AlCl.sub.3 seed
crystals, which are the building blocks for larger particles of
precipitated excess AlCl.sub.3 as described above. After the
precipitated excess AlCl.sub.3 forms, it can be separated from the
mixture and/or ionic liquid. The temperatures and separation
techniques discussed above with regard to metal halides in general
also apply to AlCl.sub.3.
Process for Removing Metal Halides from an Ionic Liquid in a
Crystallization Vessel
[0037] Yet another embodiment of the process involves removing
metal halides from an ionic liquid in a crystallization vessel.
This embodiment can be better understood with reference to FIG. 1,
which schematically illustrates this embodiment.
[0038] As shown in FIG. 1, the process includes feeding the ionic
liquid comprising metal halides 1 to a vessel 10 and providing
metal halide seed crystals to provide a mixture 9 comprising ionic
liquid, metal halides, and metal halide seed crystals. The process
further includes cooling the mixture 9 in the vessel 10 to provide
precipitated metal halides and removing the precipitated metal
halides from the vessel 10. Larger precipitated metal halides will
eventually settle to the bottom portion 11 of the vessel 10 where
they can exit the vessel 10, for example, in an effluent stream 2
comprising such precipitated metal halides.
[0039] The metal halide seed crystals can be provided by cooling,
outside addition of metal halide seed crystals, or a combination
thereof. The source of the metal halide seed crystals can depend
upon whether the process is batch or continuous.
[0040] The cooling can be achieved by internally cooling the vessel
contents (e.g. by a cooling jacket), externally cooling the vessel
contents (e.g. by an external cooling loop), or a combination of
both internally and externally cooling the vessel contents.
[0041] The vessel 10 can be constructed such that it allows for
removal of a least a portion of the mixture, from an upper portion
12 of the vessel 10; cooling the portion in a heat exchanger 4; and
reintroducing the portion into the vessel 10. In FIG. 1, the
portion that is removed from the mixture 9 is labeled as stream 3
and the cooled portion that is reintroduced into the vessel 10 is
labeled as stream 7. Such an external cooling loop 20 can provide
certain advantages. Removing mixture from the upper portion 12 of
the vessel 10 ensures a large amount of rather small metal halide
particles, rather than large metal halide particles, enter the
external cooling loop 20. Additional metal halide precipitation
occurs upon cooling of the removed portion. The small metal halide
particles act as seed crystals such that metal halide dissolved in
the ionic liquid precipitates onto these particles thereby
providing larger precipitated particles. Dissolved metal halide
precipitates onto these small metal halide particles rather than
the heat exchanger walls. Furthermore, the reintroduction of the
portion can agitate the mixture in the vessel and prevent seed
crystals from adhering the walls of the vessel.
[0042] The removed portion 3 can be filtered prior to cooling the
removed portion. In FIG. 1, such a filtering step occurs in a
filter 5. Filtering the removed portion 3 prevents any large metal
halide particles from entering the external cooling loop 20. The
removed portion 3 subjected to filtration provides a filtered,
removed portion 6, which can then be cooled in the heat exchanger 4
to provide the cooled, removed portion 7, which is reintroduced to
the vessel 10.
[0043] The reintroduction or recycle rate of the cooled, removed
portion 7 into the vessel 10 should be significant. For example,
the cooled, removed portion 7 can be reintroduced into the vessel
10 at a rate between about 5 and about 50 times the feed rate of
the ionic liquid. In one embodiment, the cooled, removed portion 7
can be reintroduced into the vessel 10 at a rate between about 10
and about 20 times the feed rate of the ionic liquid. Such a
significant recycle rate is beneficial because it provides a high
heat transfer coefficient, reduces the required temperature change
of the removed portion in the heat exchanger, and sweeps
precipitate from the heat exchanger walls thereby reducing coating
of the heat exchanger walls.
[0044] Over time, the walls of the heat exchanger could become
coated with precipitated solid and will need to be cleaned.
Therefore, it is desirable to use a duplicate spare heat exchanger
in the process for removing metal halides from an ionic liquid.
When coating of precipitate on the heat exchanger walls reduces
heat transfer below a lower acceptable limit, flow of the removed
portion to the heat exchanger can be stopped and switched to the
duplicate spare heat exchanger. Then the first heat exchanger can
be cleaned. After cleaning, flow of the removed portion to the
duplicate spare heat exchanger can be stopped and resumed in the
first heat exchanger. In this manner, the process can run without
interruption.
[0045] To prevent deposition of precipitate on heat exchanger
walls, they can be treated to reduce nucleating sites. For example,
the heat exchanger walls can be polished or coated with a smooth
material.
[0046] The feed of ionic liquid containing metal halides may also
be pre-cooled before it enters the crystallization vessel.
Pre-cooling the feed can be accomplished by pre-mixing it with the
cooled, removed portion or bringing the feed and the cooled,
removed portion into close contact.
[0047] The vessel can be jacketed for cooling and/or heating. A
cooling and/or heating jacket, shown in FIG. 1 as item 8, is useful
to provide additional cooling, adjust for any heat transfer to or
from the surroundings, maintain the vessel walls slightly warmer
than its contents to prevent precipitation on the vessel walls, and
remove precipitate from the vessel walls during cleaning.
[0048] The mixture 9 can be agitated by any known agitation method
provided that the agitation method does not destroy the metal
halide seed particles present in the mixture 9. For example, as
shown in FIG. 1, an impeller 13 can agitate the mixture 9. Flow of
the mixture 9 within the vessel 10 can also be regulated by any
known flow regulation method. For example, as shown in FIG. 1,
baffles 14 can regulate flow of the mixture 9.
Alkylation Process
[0049] Another embodiment as described herein relates to an
alkylation process, which utilizes the above-described metal halide
(e.g. AlCl.sub.3) precipitation process. The alkylation process
first involves conducting an alkylation reaction with an ionic
liquid catalyst to provide a product and a spent ionic liquid
catalyst. The spent ionic liquid catalyst is then reacted with
aluminum to provide a regenerated ionic liquid catalyst and excess
AlCl.sub.3. The excess AlCl.sub.3 is precipitated from the
regenerated ionic liquid catalyst to provide precipitated excess
AlCl.sub.3, which is removed from the regenerated ionic liquid
catalyst. The regenerated ionic liquid catalyst is recycled to the
alkylation reaction.
[0050] The following examples are provided to further illustrate
the present process and the advantages thereof. The examples are
meant to be only illustrative, and not limiting.
EXAMPLES
Example 1
Precipitation of AlCl.sub.3 from Regenerated Ionic Liquid
Catalyst
[0051] A 300 cc autoclave was charged with 50.60 gm spent ionic
liquid catalyst (n-butyl pyridinium chloroaluminate) containing
24.3 wt % conjunct polymers (acid soluble oils), 65 gm anhydrous
normal hexane and 8 gm aluminum powder. The autoclave was sealed
and heated to 100.degree. C. for 90 minutes to reactivate the
catalyst. At the end of the heating period, the autoclave and its
contents were cooled to room temperature. The top organic layer
(immiscible in the ionic liquid phase), containing the liberated
conjunct polymers, was separated from the ionic liquid by
decantation. The ionic liquid phase was rinsed with additional
hexane (2.times.50 ml) to ensure the removal of all liberated
conjunct polymers. The organic rinses were combined and
concentrated under a pressure on a rotary evaporator to give 10.5
gm of conjunct polymers as reddish viscous oil. The ionic liquid
layer (regenerated ionic liquid catalyst) was filtered in a glove
box (oxygen and moisture free environment) to separate the catalyst
from excess aluminum powder. The regenerated catalyst was obtained
in 33 gm as clear amber liquid. A small aliquot (10 gm) of the
regenerated ionic liquid was hydrolyzed with excess water and then
extracted with hexane. The hexane layer was dried over anhydrous
magnesium sulfate (MgSO.sub.4), filtered and concentrated to
retrieve any residual conjunct polymers that may have remained in
the catalyst. Only 0.07 gm conjunct polymers remained in the test
sample. The remainder of the regenerated catalyst was transferred
to a vial and kept in the glove box at room temperature. A few
hours later, the catalyst was checked and a fine off-white powder
(aluminum trichloride) had settled at the bottom of the vial. The
same observation was seen in several regeneration experiments.
Example 2
Recrystallization of Added AlCl.sub.3 from Fresh Ionic Liquid
Catalyst
[0052] To 20 gm of freshly-made ionic liquid catalyst
(n-butyl-pyridinium chloroaluminate) with an Al/N ratio of 2, 6.7
wt % AlCl.sub.3 was added and dissolved by heating the catalyst to
100.degree. C. The mixture was allowed to cool gradually to room
temperature. The added AlCl.sub.3 started to crash out of the
catalyst soon after the cooling started and completely precipitated
out within 2.5 hours.
Example 3
Recrystallization of Added AlCl.sub.3 from Fully Regenerated
Catalyst
[0053] To 20 gm of fully regenerated n-butyl-pyridinium
chloroaluminate ionic liquid catalyst containing <0.2 wt %
conjunct polymers, 6.7 wt % AlCl.sub.3 was added and dissolved by
heating the catalyst to 100.degree. C. The mixture was allowed to
cool off gradually at room temperature. The added AlCl.sub.3
started to crash out of the catalyst soon after the cooling started
and completely precipitated out within 4 hours. Accordingly, the
precipitation of added aluminum trichloride from the fully
regenerated catalyst seems to behave similarly to the freshly-made
catalyst.
Example 4
Recrystallization of Added AlCl.sub.3 from Partially Regenerated
Catalyst
[0054] To 30 gm of partially regenerated n-butyl-pyridinium
chloroaluminate ionic liquid catalyst containing .about.2 wt %
conjunct polymers, 9.8 wt % AlCl.sub.3 was added and dissolved by
heating the catalyst to 100.degree. C. The mixture was allowed to
cool off gradually at room temperature. The added AlCl.sub.3
started to precipitate out of the catalyst very slowly. It took
several hours to visibly see AlCl.sub.3 precipitation at the bottom
of the vial. It took nearly 72 hrs for .about.75% of the added
AlCl.sub.3 to precipitate out as determined by filtering the
precipitated solids out.
[0055] In comparison to Example 3, Example 4 shows that the process
for removing metal halides from an ionic liquid as described herein
is not as useful and efficient with partially regenerated ionic
liquid catalyst. Rather, the process is more useful and efficient
with fully regenerated ionic liquid catalyst.
Example 5
Continuous Crystallization of AlCl.sub.3 from Regenerated Ionic
Liquid Catalyst
[0056] Crystallization of AlCl.sub.3 from regenerated catalyst was
performed in a continuous crystallization unit. An ionic liquid
solution containing 0.1 wt % conjunct polymers (CP) and 6 wt % of
AlCl.sub.3 was prepared prior to the experiment by adding 33.2 g of
AlCl.sub.3 powder with 99.999% purity into 350 ml of regenerated
ionic liquid catalyst. The prepared ionic liquid solution was then
charged into the continuous crystallization unit, which consisted
of a 200 ml ChemGlass crystallizer equipped with a 1.5 inch
diameter overhead stirrer and heating/cooling jacket, a tubing
pump, and a 250 ml flask as catalyst reservoir above a heating
mantle. Tubes connecting these items were wrapped with heating
tape. A Lasentec.RTM. FBRM probe manufactured by Mettler-Toledo was
used for particle size distribution measurement.
[0057] The crystallization experiments were conducted at 4.degree.
C. and atmospheric pressure with overhead stirring at 400 RPM. From
the bottom of the crystallizer, a small stream of the slurry
containing AlCl.sub.3 crystals and ionic liquid solution was
continuously withdrawn and pumped by the tubing pump to the
catalyst reservoir. AlCl.sub.3 crystals in this stream were
dissolved back into the ionic liquid solution by heating the tubes
and the catalyst reservoir to 180.degree. F., which was well above
the temperature needed to dissolve 6 wt % AlCl.sub.3 in ionic
liquid. This ionic liquid solution which was free of AlCl.sub.3
crystals was fed back to the crystallizer as feed. The
recirculation flow rate was carefully controlled by the pump and
resulted in a residence time of 6 hours in the crystallizer.
[0058] The particle size distribution of the AlCl.sub.3 crystals
was monitored and recorded continuously by the FBRM probe. FIG. 2
shows the particle size distribution measured by the FBRM probe
when the system reached a steady state.
[0059] Although the present processes have been described in
connection with specific embodiments thereof, it will be
appreciated by those skilled in the art that additions, deletions,
modifications, and substitutions not specifically described may be
made without departing from the spirit and scope of the processes
as defined in the appended claims.
* * * * *