U.S. patent application number 09/442873 was filed with the patent office on 2002-12-12 for biphasic catalysis in water/carbon dioxide micellar systems.
Invention is credited to JACOBSON, GUNILLA B., JOHNSTON, KEITH P., TUMAS, WILLIAM.
Application Number | 20020188160 09/442873 |
Document ID | / |
Family ID | 26806595 |
Filed Date | 2002-12-12 |
United States Patent
Application |
20020188160 |
Kind Code |
A1 |
JACOBSON, GUNILLA B. ; et
al. |
December 12, 2002 |
BIPHASIC CATALYSIS IN WATER/CARBON DIOXIDE MICELLAR SYSTEMS
Abstract
A process is provided for catalyzing an organic reaction to form
a reaction product by placing reactants and a catalyst for the
organic reaction, the catalyst of a metal complex and at least one
ligand soluble within one of the phases of said aqueous biphasic
system, within an aqueous biphasic system including a water phase,
a dense phase fluid, and a surfactant adapted for forming an
emulsion or microemulsion within the aqueous biphasic system, the
reactants soluble within one of the phases of the aqueous biphasic
system and convertible in the presence of the catalyst to a product
having low solubility in the phase in which the catalyst is
soluble; and, maintaining the aqueous biphasic system under
pressures, at temperatures, and for a period of time sufficient for
the organic reaction to occur and form the reaction product and to
maintain sufficient density on the dense phase fluid, the reaction
product characterized as having low solubility in the phase in
which the catalyst is soluble.
Inventors: |
JACOBSON, GUNILLA B.; (LOS
ALAMOS, NM) ; TUMAS, WILLIAM; (LOS ALAMOS, NM)
; JOHNSTON, KEITH P.; (AUSTIN, TX) |
Correspondence
Address: |
BRUCE H COTTRELL
LC BPL MS D412
LOS ALAMOS NATIONAL LABORATORY
LOS ALAMOS
NM
87545
|
Family ID: |
26806595 |
Appl. No.: |
09/442873 |
Filed: |
November 18, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60109079 |
Nov 18, 1998 |
|
|
|
Current U.S.
Class: |
568/451 |
Current CPC
Class: |
C07C 45/50 20130101;
C07B 61/00 20130101; C07C 45/294 20130101; C07C 45/50 20130101;
C07C 47/02 20130101; C07C 5/03 20130101 |
Class at
Publication: |
568/451 |
International
Class: |
C07C 045/00 |
Goverment Interests
[0002] This invention was made with government support under
Contract No. W-7405-ENG-36 awarded by the U.S. Department of
Energy. The government has certain rights in the invention.
Claims
What is claimed is:
1. A process for catalyzing an organic reaction to form a reaction
product comprising: placing reactants and a catalyst for the
organic reaction within an aqueous biphasic system including a
water phase, a dense phase fluid, and a surfactant adapted for
forming an emulsion or microemulsion of said aqueous biphasic
system, the catalyst comprised of a metal complex and at least one
ligand soluble within one of the phases of said aqueous biphasic
system whereby the catalyst is soluble within one of the phases of
said aqueous biphasic system, said reactants soluble within one of
the phases of said aqueous biphasic system and convertible in the
presence of the catalyst to a product having low solubility within
the phase of said aqueous biphasic system in which the catalyst is
soluble; and, maintaining said aqueous biphasic system under
pressures, at temperatures, and for a period of time sufficient for
said organic reaction to occur and form said reaction product and
to maintain sufficient density on said dense phase fluid, said
reaction product characterized as having low solubility within the
phase of said aqueous biphasic system in which the catalyst is
soluble.
2. The process of claim 1 wherein said dense phase fluid is liquid
carbon dioxide or supercritical carbon dioxide.
3. The process of claim 1 wherein said dense phase fluid is
selected from the group consisting of a hydrocarbon, a
fluorocarbon, a fluorohydrocarbon, a substituted fluorocarbon, a
substituted fluorohydrocarbon, an ether, and carbon dioxide.
4. The process of claim 2 wherein said aqueous/carbon dioxide
biphasic system is organic-solvent free.
5. The process of claim 1 wherein the metal complex includes a
transition metal. selected from the group consisting of cobalt,
rhodium, iridium, ruthenium, osmium, molybdenum, tungsten, nickel,
palladium and platinum.
6. The process of claim 5 wherein the transition metal is selected
from the group consisting of cobalt, rhodium, iridium, ruthenium,
osmium, molybdenum, tungsten, nickel, palladium and platinum.
7. The process of claim 1 wherein said catalyst is water-soluble
and includes ligands selected from the group of sulphonated
arylphosphines, ionic phosphines, cationic phosphines, and polar
neutral phosphines, amines, and oxygen-containing ligands.
8. The process of claim 7 wherein said catalyst includes chiral
ligands.
9. The process of claim 1 wherein said catalyst is dense phase
fluid-soluble and includes ligands characterized as providing
solubility in the dense phase fluid.
10. The process of claim 2 wherein said catalyst is carbon
dioxide-soluble and includes lipophilic ligands selected from the
group of non-polar fluorinated arylphosphines, non-polar
fluorinated alkylphosphines, and siloxane-containing
phosphines.
11. A reaction mixture useful for carrying out a catalyzed organic
reaction, said mixture comprising: an aqueous biphasic system
including a water phase, a dense phase fluid, and a surfactant
adapted for forming an emulsion or microemulsion within said
aqueous biphasic system; a reactant for said organic reaction, said
reactant soluble within one of the phases of the biphasic system;
and a catalyst for said organic reaction, said catalyst comprised
of a metal complex with at least one ligand soluble within one of
the phases of said aqueous biphasic system whereby the catalyst is
soluble within one of the phases of said aqueous biphasic
system.
12. The reaction mixture of claim 11 wherein said dense phase fluid
is liquid carbon dioxide or supercritical carbon dioxide.
13. The reaction mixture of claim 11 wherein said dense phase fluid
is selected from the group consisting of a hydrocarbon, a
fluorocarbon, a fluorohydrocarbon, a substituted fluorocarbon, a
substituted fluorohydrocarbon, an ether, and carbon dioxide.
14. The reaction mixture of claim 11 wherein said metal complex
includes a transition metal. selected from the group consisting of
cobalt, rhodium, iridium, ruthenium, osmium, molybdenum, tungsten,
nickel, palladium and platinum.
15. The reaction mixture of claim 14 wherein said transition metal
is selected from the group consisting of cobalt, rhodium, iridium,
ruthenium, osmium, molybdenum, tungsten, nickel, palladium and
platinum.
16. The reaction mixture of claim 11 wherein said catalyst is
water-soluble and includes ligands selected from the group of
sulphonated arylphosphines, ionic phosphines, cationic phosphines,
and polar neutral phosphines, amines, and oxygen-containing
ligands.
17. The reaction mixture of claim 16 wherein said catalyst includes
chiral ligands.
18. The reaction mixture of claim 11 wherein said catalyst is dense
phase fluid-soluble and includes ligands characterized as providing
solubility in the dense phase fluid.
19. The reaction mixture of claim 11 wherein said catalyst is
carbon dioxide-soluble and includes lipophilic ligands selected
from the group of non-polar fluorinated arylphosphines, non-polar
fluorinated alkylphosphines, and siloxane-containing
phosphines.
20. The reaction mixture of claim 11 wherein said organic reaction
is hydroformylation, said reactant is an olefin, diene or polyene
and said reaction mixture further includes hydrogen and carbon
monoxide to produce an aldehyde or a derivative thereof.
21. The reaction mixture of claim 20 wherein said olefin is
selected from the group consisting of olefins, dienes and
polyenes.
22. The reaction mixture of claim 16 wherein said catalyst is a
transition metal based catalyst.
23. The reaction mixture of claim 11 wherein said organic reaction
is hydrogenation, said reactant is a substrate capable of
undergoing hydrogenation and said reaction mixture further includes
hydrogen.
24. The reaction mixture of claim 23 wherein said catalyst is
water-soluble.
25. The reaction mixture of claim 23 wherein said dense phase fluid
is carbon dioxide and said catalyst is carbon dioxide-soluble.
26. The reaction mixture of claim 23 wherein at least one
water-soluble ligand with said metal complex is a chiral
water-soluble catalyst containing an enantiomerically enriched
chiral ligand for conducting an enantioselective hydrogenation.
27. The reaction mixture of claim 11 wherein said organic reaction
is a carbon-carbon bond forming reaction and said reactant includes
a pair of substrates capable of undergoing a carbon-carbon bond
forming reaction in the presence of said catalyst.
28. The reaction mixture of claim 11 wherein said organic reaction
is oxidation, said reactant is a substrate capable of undergoing
oxidation in the presence of said catalyst, and said reaction
mixture further includes an oxidant species.
Description
[0001] The present application claims the benefit of U.S.
provisional application No. 60/109,079, filed on Nov. 18, 1998.
FIELD OF THE INVENTION
[0003] The present invention relates to catalysis in water/dense
phase fluid systems, e.g., water/carbon dioxide systems.
BACKGROUND OF THE INVENTION
[0004] Heterogeneous catalysts currently dominate the field of
large-scale industrial chemical synthesis, as the catalyst can
easily be separated and reused after the reaction is complete.
Homogeneous catalysts typically operate at milder temperatures and
can exhibit activities and selectivities unknown by their
heterogeneous counterparts, although problems associated with the
separation, recovery and re-use of typically highly expensive
homogeneous catalysts can sometimes be a limitation. Homogeneous
catalysis is, however, widely used in specialty applications, such
as production of pharmaceuticals, where high selectivity is of
great importance.
[0005] Rapid developments in the field of catalysis are leading to
an increased demand for tailor-made catalysis. Significant research
efforts have been focused upon the immobilization of the
organometallic species responsible for catalysis. There have been
many reports of "heterogenization" of homogeneous catalysts by
tethering them to solid supports such as silica, alumina,
polystyrene and water-soluble polymers. The act of supporting these
catalysts on a heterogeneous substrate often has a deleterious
effect upon their performance and, at best, the performance of such
heterogeneous catalysts only approximates those of their
homogeneous counterparts. Another disadvantage of supported
catalysts is the continuous loss of the metal (leaching) which both
contaminates the product phase and increases the production cost
due to loss of expensive catalyst.
[0006] Other research efforts have been directed to the
immobilization of a catalyst in a "mobile phase" such as an aqueous
solution immiscible with the product phase. This type of system
represents an almost ideal combination of homogeneous and
heterogeneous catalysis. Compared to a solid-supported catalyst, it
should function more like a homogeneous catalyst and show
characteristic features of a homogeneous catalyst, such as higher
reactivity, higher selectivity and better reproducibility under
mild conditions. This approach has been used in aqueous two-phase
catalysis with water-soluble catalyst complexes bearing
water-soluble ligands such as sulfonated triarylphosphines (see,
for example, U.S. Pat. No. 4,248,802 by Kuntz for catalytic
hydroformylation of olefins). The reactants can be either soluble
in the water phase or, since the number of water-soluble organic
substrates are limited, form a separate phase.
[0007] The reaction can take place across the interface, in the
water phase or in the dense fluid phase depending upon the
hydrophilicity of the reactants. The reaction rates are then
governed by the solubility of the reactant in the water, and due to
decreased solubility, reaction rates are often slower than a
single-phase homogeneous reaction. If the product is not
water-soluble, it can be easily separated from the water-soluble
catalyst complex, allowing the catalyst complex to be recycled.
[0008] Current industrial applications of water-soluble catalysts
are generally limited to substrates with significant water
solubility. The well-known Rhone-Poulenc process for
hydroformylation of propene to butanal on a scale of around 330,000
tons per year takes advantage of a water-soluble catalyst. That
process cannot be effectively extended to longer chain olefins due
to their negligible solubility in water. Mass transport limitations
for longer chain olefins across a phase boundary lead to
significantly lower reaction rates. The ability to use
water-soluble catalysts with hydrophobic or poorly water-soluble
substrates remains a major challenge, not only in the
hydroformylation of longer chain olefins, but also in catalytic
transformations of hydrophobic substrates in general.
[0009] A number of investigators have tried to overcome the mass
transfer limitations of a two-phase system by addition of either a
phase transfer catalyst (PTC) or an interfacially active
amphiphilic surfactant. In the case of a PTC (typically a
quaternary ammonium compound), a complex is generally formed
between the PTC and either (a) the catalyst in the aqueous phase
whereafter the catalyst can be transported into the organic phase,
or (b) the hydrophobic compound whereafter the hydrophobic compound
can be transported into the aqueous phase (see Starks et al., Phase
Transfer Catalysis, Chapman and Hall, New York, 1994). A major
disadvantage of using a PTC is that it further complicates the
purification step as the PTC is slightly soluble in both phases and
cannot be easily separated into the aqueous phase for recycle.
[0010] The addition of a surfactant in a two-phase system can allow
micelles of, e.g., the water phase, to be dispersed in the second
phase, typically an organic phase, which significantly increases
the surface area between the two phases, reaching values as high as
10.sup.5 square meter per liter of microemulsion. The surfactant
can also lower the surface tension between the two phases, further
promoting the reaction across the interface. Although numerous
studies of organic reactions have been reported in microemulsions
(optically transparent microheterogeneous systems with droplet
sizes from about 2 .ANG. to about 500 .ANG.), extremely few have
been reported in emulsions (milky-white opaque systems with droplet
sizes greater than about 500 .ANG.), with the exception of
heterogeneous polymerizations. The difficulty in breaking an
emulsion or microemulsion composed of water and an organic solvent
is a formidable problem. Another problem with microemulsions is
that it is often necessary to add a cosolvent to achieve the proper
balance of attractive and repulsive interactions on the hydrophobic
and hydrophilic sides of the interface. While the cosolvent can
reduce the interfacial tension between the droplets and the
continuous phase, it can cause further separation problems.
[0011] Other recent approaches have been reported to overcome mass
transfer limitations using organic solvents in biphasic catalysis.
In one approach, Horvath et al., U.S. Pat. No. 5,463,082, describe
catalysts that are soluble in fluorocarbons. Heating these systems
in a fluorocarbon and hydrocarbon solvent mixture leads to a
miscible homogeneous reaction mixture, which can be separated into
two phases, a hydrocarbon/product phase and a fluorocarbon/catalyst
phase, upon cooling after reaction.
[0012] Recently, micellar solutions of water in supercritical
carbon dioxide were reported (see, Johnston et al., Science, vol.
271, pp. 264, 1996). Supercritical fluids (i.e., the state of a
compound when it is at or above its critical temperature and
critical pressure) have liquid-to-gas like densities, higher
diffusivities and lower viscosities, all due to the highly
compressable nature of the fluid. There are also literature reports
of using supercritical fluids, especially supercritical carbon
dioxide, as solvents in homogeneous catalysis. In U.S. Pat. No.
5,198,589 by Rathke et al., cobalt carbonyl catalyzed
hydroformylation was conducted in a single phase reaction medium of
supercritical carbon dioxide. Carbon dioxide is an attractive
alternative to organic solvents as it is environmentally benign,
essentially nontoxic, inexpensive, nonflammable, has low critical
conditions (P.sub.c=73.8 bar, T.sub.c=31.degree. C.) and can be
easily recycled. Supercritical fluids also share many of the
advantages of gases including miscibility with other gases, low
viscoisity, and high diffusivities, thereby providing enhanced heat
transfer and the potential for faster reactions, particularly
diffusion controlled reactions involving gaseous reactants such as
hydrogen, oxygen and carbon monoxide. The density of the fluid,
which may be adjusted with temperature and pressure, has a large
effect on the solvation of the surfactant tail, and thus the phase
behavior and stability of the microemulsion or emulsion. Density
effects on water-in-supercritical fluid microemulsions have been
explained experimentally and theoretically. The interfacial
tension, (.gamma.), between water and carbon dioxide (18 mNm.sup.-1
at pressures above 70 bar) is much lower as compared to water and
an organic solvent (30-50 mNm.sup.-1). This eliminates the need of
any cosolvents and also further promotes reactions across the
interface. Lower .gamma. values reflect the fact that carbon
dioxide is more miscible with water than typical non-polar
organics, largely due to the acidity and quadrupole moment of
carbon dioxide. Another important advantage of using carbon dioxide
as the dispersed phase is that emulsions are easily broken by
rapidly reducing the pressure, separating the water and carbon
dioxide into separate phases. The carbon dioxide phase can be
subsequently removed simply by vaporization. The micellar system
type, i.e., microemulsion or emulsion, is governed by the type and
amount of the surfactant, and the volume fractions of the water to
carbon dioxide.
[0013] A catalytic system or process which overcomes these
obstacles of a) separating the product from the catalyst and
recycling the latter, b) decreasing mass-transfer limitations by
micellar catalysis (i.e., increased surface area and decreased
interfacial tension), and c) when using carbon dixoide, removal of
all organic solvents for the use of environmentally benign water
and carbon dioxide has now been developed using a water/dense phase
fluid, e.g., carbon dioxide, micellar reaction system with the
catalyst complex and reaction products each soluble in a separate
phase.
[0014] It is an object of this invention to provide a process for
conducting organic reactions in an aqueous biphasic reaction system
employing a catalyst for a selected organic reaction, the catalyst
either water-soluble or dense phase fluid-soluble and the reaction
product soluble in the phase in which the catalyst is insoluble,
wherein the reaction products and catalyst can be readily separated
by a phase separation.
[0015] Another object of this invention is a process for conducting
organic reactions in an aqueous biphasic reaction system wherein
the reaction rate is enhanced by employment of an aqueous biphasic
system including a water phase, a dense phase fluid, a surfactant
adapted for forming an emulsion or microemulsion within said
aqueous biphasic system, and a catalyst for the selected organic
reaction, the catalyst comprised of a metal complex, e.g., a
transition metal complex, and at least one ligand, the ligand or
ligands soluble in either the water phase or the dense phase
fluid.
[0016] Another object of this invention is a process for conducting
organic reactions in an aqueous biphasic reaction system wherein
the reaction rate is enhanced from one or more factors such as gas
miscibility, lower surface tension, and increased surface area.
[0017] It is another object of this invention to provide an aqueous
biphasic reaction mixture including a water phase, a dense phase
fluid, and a surfactant adapted for forming an emulsion or
microemulsion within said aqueous biphasic system, and a catalyst
for a selected organic reaction, the catalyst comprised of a metal
complex, e.g., a transition metal complex, and at least one ligand,
the ligand or ligands soluble in either the water phase or the
dense phase fluid.
[0018] Still another object of this invention is to provide a
aqueous biphasic reaction mixture including a water phase, a dense
phase fluid, and a surfactant adapted for forming an emulsion or
microemulsion within said aqueous biphasic system, a catalyst for a
selected organic reaction, the catalyst comprised of a metal
complex, e.g., a transition metal complex, and at least one ligand,
the ligand or ligands soluble in either the water phase or the
dense phase fluid, and reactants for said organic reaction, the
reactants soluble within one of the phases of the biphasic
system.
[0019] Yet another object of the present invention is a process of
conducting organic reactions such as hydroformylation reactions,
hydrogenation reactions including asymmetric or enantioselective
hydrogenation reactions, carbon-carbon bond forming reactions,
oxidation reactions, and carbonylation reactions within an aqueous
biphasic system including a water phase, a dense phase fluid, a
surfactant adapted for forming an emulsion or microemulsion within
said aqueous biphasic system, and a catalyst for the selected
organic reaction, the catalyst comprised of a metal complex, e.g.,
a transition metal complex, and at least one ligand, the ligand or
ligands soluble in either the water phase or the dense phase
fluid.
SUMMARY OF THE INVENTION
[0020] To achieve the foregoing and other objects, and in
accordance with the purposes of the present invention, as embodied
and broadly described herein, the process of this invention
provides for catalyzing an organic reaction to form a reaction
product including placing reactants and a catalyst for the organic
reaction, within an aqueous biphasic system including a water
phase, a dense phase fluid, and a surfactant adapted for forming an
emulsion or microemulsion of said aqueous biphasic system, the
catalyst comprised of a metal complex and at least one ligand
soluble within one of the phases of the aqueous biphasic system,
said reactants soluble within one of the phases of said aqueous
biphasic system and convertible in the presence of the catalyst to
a product having low solubility within the phase of said aqueous
biphasic system in which the catalyst is soluble, and maintaining
said aqueous biphasic system under pressures, at temperatures, and
for a period of time sufficient for said organic reaction to occur
and form said reaction product, said reaction product characterized
as having low solubility within the phase of said aqueous biphasic
system in which the catalyst is soluble.
[0021] The present invention further provides a reaction mixture
useful for carrying out an organic reaction, said mixture including
an aqueous biphasic system including a water phase, a dense phase
fluid, and a surfactant adapted for forming an emulsion or
microemulsion within said aqueous biphasic system; a reactant for
said organic reaction, said reactant soluble within one of the
phases of the biphasic system, and a catalyst for said organic
reaction, said catalyst comprised of a metal complex and at least
one ligand soluble within one of the phases of the aqueous biphasic
system whereby the catalyst is soluble within one of the phases of
the aqueous biphasic system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 shows a schematic drawing of a biphasic micellar
system wherein the reactions of the present invention are run and
the two-phase system resulting from depressurization of the
biphasic micellar system used with the present invention.
[0023] FIG. 2 shows a variable-volume-view cell used in the
examples of the present invention.
[0024] FIG. 3 shows a time profile of formation of ethyl benzene
from hydrogenation of styrene performed in biphasic water/carbon
dioxide or carbon dioxide/water emulsions using selected
surfactants compared with typical reactions performed in biphasic
water/toluene or in biphasic water/carbon dioxide.
[0025] FIG. 4 shows a graph plotting TOF values at 50 percent
conversion for a biphasic water/toluene system (A) or in a biphasic
water/carbon dioxide system (B) and in biphasic water/carbon
dioxide emulsion system (C) as in FIG. 3.
[0026] FIG. 5 shows a graph of the yield as a function of time for
the hydrogenation of 1-octene, 1-decene and 1-eicosene.
DETAILED DESCRIPTION
[0027] The present invention is concerned with a process involving
the following items: (1) performing reactions, such as
hydroformylation, hydrogenation including asymmetric hydrogenation,
carbon-carbon bond forming (carbon coupling), carbonylation, and
oxidation reactions in an aqueous two-phase system with
water-soluble catalysts such as previously used in homogeneous
reactions thereby allowing simplified recovery of the product as
well as essentially complete recovery of the catalysts; (2)
utilizing micellar catalysis, i.e., increasing surface area and
lowering surface tension, by addition of a surfactant; and, (3)
where desirable, replacing organic solvents with an aqueous
biphasic system consisting of water and a dense phase fluid such as
carbon dioxide. The present invention is also concerned with a
process involving the following items: (1) performing reactions,
such as hydroformylation, hydrogenation including asymmetric
hydrogenation, carbon-carbon bond forming (carbon coupling),
carbonylation, and oxidation reactions in an aqueous two-phase
system with dense phase fluid-soluble catalysts and a water-soluble
reaction product thereby allowing simplified recovery of the
product as well as essentially complete recovery of the catalysts;
(2) utilizing micellar catalysis, i.e., increasing surface area and
lowering surface tension, by addition of a surfactant thereby
increasing reaction rates; and, (3) where desirable, replacing
organic solvents with an aqueous biphasic system consisting of
water and a dense phase fluid such as carbon dioxide. The present
invention is also concerned with reaction mixtures used and
produced in the processes of the present invention.
[0028] The biphasic system employed in the present invention can
contain water as the continuous phase and a dense phase fluid as
the dispersed phase or can contain a dense phase fluid as the
continuous phase and water as the dispersed phase. FIG. 1 shows a
drawing with one embodiment of a biphasic micellar system 10
wherein the reactions of the present invention are run and the
two-phase system 20 resulting from depressurization of the biphasic
micellar system used with the present invention. Biphasic micellar
system 10 includes micelles 15. In one embodiment, the water phase
serves as the catalyst-supporting phase for a water-soluble
catalyst. The product or products of such a particular organic
reaction are characterized as having low or limited water
solubility, i.e., the products or products will be partitioned
primarily into the dense phase fluid. In another embodiment, the
dense phase fluid serves as the catalyst-supporting phase for a
dense phase fluid-soluble catalyst. The product or products of such
a particular organic reaction are characterized as having low or
limited dense phase fluid solubility, i.e., the products or
products will be partitioned primarily into the water phase.
[0029] It is desirable that the catalyst ne insoluble or have
limited or low solubility in one of the phases of the biphasic
micellar system and the product or products of a particular organic
reaction to have low or limited solubility in the phase in which
the catalyst is soluble. Systems where the product or products have
higher solubility, i.e., partition to a greater extent into the
phase in which the catalyst is soluble can have value as well as
the product or products can simply remain in the phase including
the catalyst upon phase separation. However, effecient catalyst
recycle makes it especially desirable that the catalyst have as low
of solubility as possible in the phase in which the product or
products are primarily partitioned. Where the catalyst includes
precious metals or expensive ligands this is even more desirable to
avoid the loss of catalyst from the system with the product.
Generally, where the catalyst contains a non-precious metal, the
term "low or limited solubility" can generally refer to amounts of
as low as less than about 5 percent by weight, based on total
weight of catalyst in the system, while where the catalyst contains
a precious metal or expensive ligand, the term "low or limited
solubility" would preferably refer to amounts of as low as less
than about 1 percent by weight, based on total weight of catalyst
in the system.
[0030] The dense phase fluid is of a gas (at standard temperature
and pressure) that can be compressed to a liquid-like state or a
supercritical state and can be, e.g., a hydrocarbon such as
propane, ethane and the like, a halogenated hydrocarbon such as a
fluorocarbon, a fluorohydrocarbon, a substituted fluorocarbon, a
substituted fluorohydrocarbon and the like, an ether such as
dimethyl ether and the like, or carbon dioxide. Preferably, the
dense phase fluid is carbon dioxide. No additional solvent is
required with such a biphasic system including a dense phase fluid
so that the reaction system can be operated free of an organic
solvent.
[0031] Use of carbon dioxide as the dense phase fluid can have
clear advantages, i.e., it is nontoxic, nonflammable, inexpensive,
and unregulated. Additional advantages of carbon dioxide include:
(1) the surface tension, .gamma., between water and carbon dioxide
is significantly lower compared to a water/non-polar organic
solvent interface; (2) an emulsion with carbon dixoide as the dense
phase fluid is easily broken, allowing ready separation of a
water-soluble catalyst for subsequent recycle; and, (3) the
solubility and diffusivity of potential reactant gases such as
hydrogen and carbon monoxide is greater in carbon dioxide than in
non-polar organic solvents.
[0032] Typically, micelle formation in aqueous solution can be
promoted by molecules which contain a long chain (greater than 10
atoms in the chain backbone) hydrophobic alkyl group, and such a
long chain hydrophobic alkyl group including heteroatoms other than
carbon such as oxygen, sulfur, nitrogen and fluorine or the like,
and contain a hydrophilic, ionic head-group (such as tetraalkyl
ammonium or sulfonate) at one end. Micelle formation may also be
promoted by neutral molecules, which possess a long-chain alkyl
group as a hydrophobic group in combination with a hydrophilic
segment such as a hydroxyl-terminated polyethylene glycol. There
are four major classes of surfactants available: anionic, cationic,
neutral and amphoteric.
[0033] The process of the present invention can be operated at
temperatures and pressures such that the dense phase fluid is in
the liquid phase or is a supercritical fluid. With the dense phase
fluid, the choice of the temperature at which the particular
organic reaction is optimally run will determine whether the dense
phase fluid is a liquid or is a supercritical fluid. When the
desired temperature is above the supercritical temperature of dense
phase fluid, the system would likely be comprised of a
supercritical phase as the non-aqueous phase.
[0034] Several surfactants are known to form microemulsions and
emulsions of water and dense phase carbon dioxide.
Perfluoropolyether ammonium carboxylate (PFPE) shown below 1
[0035] is one example of a anionic surfactant which can be used.
Poly(butylene oxide)-b-poly(ethylene oxide) (PBO-b-PEO) shown below
2
[0036] is an example of a non-ionic surfactant which can be used.
PFPE is commercially available in the COOH form (e.g., from
Ausimont under the tradename Fomblin MF300) and can have average
molecular weights ranging from about 600 to about 2500 or more. Use
of PFPE as the surfactant can allow formation of both water in
carbon dioxide or carbon dioxide in water microemulsions, and water
in carbon dioxide or carbon dioxide in water emulsions. Use of
PBO-b-PEO as the surfactant allows only the formation of emulsions.
Other poly(propylene oxide)- and poly(butylene oxide)-based
surfactants as described by Johnston et al. in U.S. Pat. No.
5,733,964 may be employed as the surfactants in the present
invention. An example of a cationic surfactant considered suitable
in the present invention is a fluorochemical cationic surfactant
available from Ciba Specialty Chemicals Corporation under the
tradename of Lodyne S-106A shown below. 3
[0037] An example of a PBO-b-PEO type non-ionic surfactant
considered suitable in the present invention is available from PPG
Industries, Inc. under the tradename SAM-185. Other surfactants
capable of forming micelles in a reaction mixture of water and
carbon dioxide would be suitable as well and such surfactants will
be readily apparent to those skilled in the art.
[0038] With the use of various surfactants with PFPE and
poly(dimethylsiloxane) (PDMS) tails, the interfacial tension
between water and carbon dioxide may be reduced to 1 mNm.sup.-1,
which is sufficiently low to form emulsions or microemulsions.
Variations in the chemical structure of the siloxyl monomer of PDMS
(i.e. the second component of the copolymer) include ethylene
oxide/propylene oxide modified siloxyl monomer, carboxylate
modified monomer, and alkane modified monomer.
[0039] Surfactant concentrations in the reaction mixtures of the
present invention generally range from about 0.1 weight percent, on
the basis of the total weight of the reaction mixture, up to about
50 weight percent. Preferably, the surfactant concentrations in the
reaction mixtures range from about 0.1 weight percent to about 15
weight percent, and more preferably from about 0.1 weight percent
to about 3 weight percent. Higher concentrations of surfactant can
be employed where it is desirable to have higher
water-to-surfactant values, W.sub.o. W.sub.o refers to the mole
ratio of water to surfactant.
[0040] The weight percent of water to dense phase fluid, preferably
carbon dioxide, in the reaction mixtures of the present invention
determines whether the reaction mixture forms a microemulsion or an
emulsion. The weight percent of water generally ranges from about
0.1 weight percent to about 50 weight percent. Higher weight
percentages generally result in the formation of emulsions.
[0041] Useful catalysts for the processes of the present invention,
such as hydroformylation reactions, hydrogenation reactions,
carbonylation reactions, oxidation reactions and carbon-carbon bond
forming reactions, can include transition metals. Such transition
metals can be selected from the group of cobalt, rhodium, iridium,
ruthenium, osmium, molybdenum, tungsten, nickel, palladium and
platinum. Other transition metals such as zinc and other metals
such as aluminum may also be included in catalysts. Catalysts can
be made water-soluble by using water-soluble ligands. Such
water-soluble ligands can be chiral ligands or achiral ligands such
as generally described by Chao-Jun Li et al. in Organic Reactions
in Aqueous Media, John Wiley & Sons, Inc. (1997) and especially
section 5.1 at pages 116-123 on Water-Soluble Ligands, such
description incorporated herein by reference. Catalysts can be made
dense phase fluid-soluble by using dense phase fluid -soluble
ligands. Such dense phase fluid-soluble ligands can be, e.g.,
non-polar fluorinated arylphosphines, non-polar fluorinated
alkylphosphines, and siloxane-containing phosphines. Exemplary
dense phase fluid-soluble ligands include
tris[3,5-bis(trifluoromethyl)phenyl]phosphine and the like or
PRR'R.sub.f and PRR'OR.sub.f where R.sub.f is
CH.sub.2CH.sub.2C.sub.6F.sub.13 and R and R' are cyclohexyl or
phenyl. Such dense phase fluid-soluble catalysts can be made by a
ligand exchange of such mentioned ligands with, e.g.,
chloro(1,5-cyclooctadiene)rhodium(I- ) dimer or
chloro(cyclooctene)rhodium(I) dimer in dichloromethane. Other
ligands and transition metals may also be used.
[0042] One of the most commonly used groups of water-soluble
ligands are sulfonated arylphosphines such as mono-sulfonated
triphenylphosphines (tppms), di-sulfonated triphenylphosphines
(tppds-shown below), 4
[0043] or tri-sulfonated triphenylphosphines (tppts). Amphiphilic
ligands, i.e., ligands including two types of groups within the
ligand, may be employed as well. Also, ligands tethered to surface
active agents may be employed as well, such as those described by
Hanson et al. in Catalysis Today, vol. 42, pp. 421-429 (1998), such
description incorporated herein by reference. Other water soluble
ligands (including anionic, cationic, nonionic, and chiral) can
also be applied, such as amphos
((C.sub.6H.sub.5).sub.2PCH.sub.2CH.sub.2N(CH.sub.3).sub.3.sup.+I.sup.-)
and BINAS (sulphonated
2,2'-bis(diphenylphosphinomethyl)-1,1"-binaphthyl-- -shown below).
5
[0044] Still other water-soluble ligands will be apparaent to those
of skill in the art.
[0045] For hydroformylation reactions and hydrogenation reactions,
the well-known water soluble RhCl(tppds).sub.3 catalyst is
especially preferred where tppds is a disulphonated
triphenylphosphine ligand. This rhodium catalyst complex can be
obtained by a simple ligand exchange with the original Wilkinson's
catalyst, RhCl(PPh.sub.3).sub.3, following the process of equation
(1).
RhCl(P(C.sub.6H.sub.5).sub.3).sub.3+6tppds.fwdarw.RhCl(tppds).sub.3X3tppds-
+3P(C.sub.6H.sub.5).sub.3 Equation (1)
[0046] For carbon-carbon bond forming reactions, the known
PdCl.sub.2(tppds).sub.2 catalyst can be used, obtained by ligand
exchange with PdCl.sub.2(PhCN).sub.2, following the process of
equation (2).
PdCl.sub.2(C.sub.6H.sub.5CN).sub.2+2tppds.fwdarw.PdCl.sub.2(tppds).sub.2+2-
C.sub.6H.sub.5CN Equation (2)
[0047] Chiral water-soluble ligands such as shown below 6
[0048] can be synthesized and used for asymmetric hydrogenations,
and should give similar results to the standard hydrogenation
process. Many other water-soluble catalyst systems may be employed
as will be readily apparent to those skilled in the art.
[0049] In the catalyst complex, the amount of metal to
water-soluble ligand is generally at a ratio of at least 1:1, and
as an excess of ligand is preferred may be generally desirable. In
the case of hydroformylation reactions, the ratio is preferably
from about 1:6 as addition of higher levels of ligand generally
will result in a higher straight chain to branched chain (n/i)
product ratio.
[0050] The catalyst concentration for a process of the present
invention is generally from about 0.1 mole percent, on the basis of
the total weight of substrate (reactant) and catalyst, to about 15
mole percent. More preferably, the catalyst concentration is from
about 1 mole percent to about 10 mole percent for higher production
rates of product.
[0051] The reactants for the organic reaction are soluble in either
the aqueous phase (water) or in the dense phase fluid.
[0052] Various classes of catalytic reactions are possible for
reaction following the general process presented in the present
invention. Such catalytic reactions include hydroformylations,
hydrogenations including asymmetric hydrogenations, carbonylations,
carbon-carbon bond forming reactions, and oxidation reactions.
Other catalytic reactions that may be run in a process in
accordance with the present invention will be readily apparent to
those skilled in the art.
[0053] Hydroformylations (shown by equation (3)), hydrogenations
(shown by equation (4)) and carbon-carbon bond forming reactions
(shown by equation (5)) of non water-soluble substrates are some of
the reactions that can be conducted using the process and reaction
mixtures of the present invention.
[0054] (3) Hydroformylation 7
[0055] (4) Hydrogenation 8
[0056] where, R, R', R", R'" can be H, CO.sub.2R, NO.sub.2, CN,
COR
[0057] (5) Carbon-Carbon Bond Forming Reactions, e.g.,
[0058] ((A)--the Heck reaction, Palladium catalyzed arylation and
alkylation of olefins); 9
[0059] ((B) Suzuki Coupling: Palladium catalyzed arylation and
vinylation of boronic acids); and 10
[0060] ((C) Stille Coupling: Palladium catalyzed arylation and
vinylation with organotrichloro-stannanes) 11
[0061] R=aryl, vinyl; X=I, Br, COCl, OTf (triflate), and the
like.
[0062] (6) Carbonylations
[0063] a) 12
[0064] X=halide; Nu=nucleophile
[0065] and, b) 13
[0066] (7) Oxidations 14
[0067] (8) Asymmetric Hydrogenations 15
[0068] For hydroformylations, the substrates can be olefins, e.g.,
more specifically, ethylenically unsaturated compounds generally
including one or more double bonds, one of which can be a terminal
double bond, and having from 2 to 20 or more carbon atoms. The
substrate can be a diene or a polyene. The process of the present
invention can be especially useful for such substrates containing
greater than six carbon atoms. Hydroformylation products of such
larger olefins are characterized as having limited solubility in
water. Such larger olefins include, e.g., 1-heptene, 1-octene,
1-nonene, 1-decene, 6-propyl-1-decene, 3-undecene, 1-dodecene,
1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene,
1-octadecene, 1-nonadecene, styrene and the like.
[0069] Hydroformylation reactions conducted in accordance with the
present invention can utilize partial pressure of carbon monoxide
and hydrogen such that the molar ratio of carbon monoxide to
hydrogen varies from about 0.1 to about 10. Preferably a molar
ratio from about 0.15 to about 0.7 is used. The pressure of the
carbon monoxide and hydrogen introduced into the system is
generally from about 50 psi to about 350 psi. Additonal pressure in
the high pressure system is supplied by the dense phase fluid,
e.g., by carbon dioxide. The total pressure in the system is
generally from about 1000 psi to about 7500 psi.
[0070] The substrate concentrations can generally be as high as is
permitted in the particular system. The amount of substrate depends
upon the overall micellar system with the greatest amount of
substrate that is soluble but still able to form micelles. Higher
concentrations are generally preferred for greater output. A 1
Molar (M) concentration of the substrate typically would be high
with a range of concentration generally being from about 10
milliMolar (mM) up to 1 M or higher.
[0071] Reaction conditions in the process of the present invention
include a temperature range of from about 10.degree. C. to about
200.degree. C. The temperature must be maintained below the
decomposition temperature of any reaction mixture component or any
product of the reaction. The temperature for many reactions is
often above the critical temperature of supercritical carbon
dioxide, i.e., about 31.degree. C. Optimal pressure for the process
of the present invention is above the cloud point of the reaction
system. The total pressure in the present invention is generally
from about 1000 psi to about 7500 psi.
[0072] Results are shown for (i) surfactant-free two-phase systems
(a system including only water and carbon dioxide), and for (ii) a
system including water, carbon dioxide and a surfactant for
formation of a microemulsion or emulsion. The data presented below
is for some typical non water-soluble substrates, but these
reactions can be extended to more complex substrates as well.
[0073] An example of hydroformylation of a non water-soluble
compound is the hydroformylation of 1-decene. The substrate is
soluble in supercritical carbon dioxide, as are the two major
products, 1-undecanal and 2-methyl decanal. The former product is
of interest for perfumery chemicals. The ratio of ligand/Rh is
known to effect the ratio of linear to branched aldehyde obtained.
A value greater than four increases the amount of linear aldehyde,
which is the more desirable product.
[0074] In the process of the present invention, the reactions can
be performed in a variable-volume-cell equipped with a sapphire
window for visual inspection of the solvent system. Reactants can
be injected into the cell and samples can be taken out of the cell
through a 6-port sampling valve. The pressure in the cell can then
be adjusted accordingly by an ISCO syringe pump, which is connected
directly to the back of the piston in the cell. A pump can be used
to recirculate the fluid phase in the cell and together with a
stirbar inside the cell enough shear can be obtained to form the
micellar phase.
[0075] Other reaction cells can be employed as well, including
tubes, pipes, autoclaves, and the like. The process can be operated
as a continuous flow process or a batch process or by any other
suitable process apparent to those of skill in the art.
[0076] Under an inert atmosphere such as nitrogen, argon or the
like, the reactor can be loaded from the front end with surfactant,
water, catalyst and an internal standard. The reactor can then be
closed, removed from the inert atmosphere and connected to the pump
and gas lines. The reactant gases (hydrogen and carbon monoxide),
if used, can be added followed by the desired amount of carbon
dioxide. The reactor can be heated in any appropriate fashion,
connected to a temperature controller, and pressurized by adding
carbon dioxide to the back side of the piston. While heating the
cell, the piston can move back accordingly, assuring a constant
pressure inside of the cell, and the pump and stir plate can be
activated. Once the desired temperature and pressure are achieved
inside the cell, the substrate can be injected via the sample loop
on the 6-port valve, indicating the start of the particular
reaction.
[0077] While not wishing to be bound by the present explanation, it
is believed that during the reaction the catalyst is located inside
the aqueous micelles and the substrate and products are dissolved
in the carbon dioxide phase. After depressurizing the system (by
releasing the pressure on the piston thereby moving it back to
expand the volume and also decreasing the temperature), the
micellar system can be broken and a two phase system obtained,
consisting of a lower aqueous phase and a carbon dioxide phase,
separated by a surfactant layer. The carbon dioxide phase can then
be vented from the cell., allowing the products to be collected by
tuning the density (i.e., solvent power) of the carbon dioxide
phase, as will be readily apparent to those skilled in the art. The
vaporized carbon dioxide can be collected and recycled. The
surfactant and aqueous catalyst phase are left behind in the
reactor, which are reused in the next experiment.
[0078] The present invention is more particularly described in the
following examples, which are intended as illustrative only, since
numerous modifications and variations will be apparent to those
skilled in the art.
[0079] FIG. 2 shows a variable-volume-view cell 25 used in the
examples of the present invention, the cell including piston 30,
syringe 32, pump 34, and gas lines 36 and 38.
EXAMPLE 1
[0080] Hydroformylation reactions were performed as follows. Under
a nitrogen atmosphere, pairs of cells were loaded from the front
end with the selected surfactant (0.5 weight percent SAM-185 for
the emulsion based on the total weight of water and carbon dioxide,
1.4 weight percent PFPE for the microemulsion based on total weight
of water and carbon dioxide, or no surfactant in the case of the
two-phase comparison runs performed side-by-side with the
surfactant-containing systems), water (4.75 g for the emulsion and
comparison run and 75 milligrams (mg) for the microemulsion and
comparison run), catalyst (RhCl(tppds).sub.3 or BINAS) and an
internal standard of nonane. The cells were sealed, removed from
the nitrogen atmosphere and connected to the pump and gas lines.
The reactant gases of hydrogen and carbon monoxide were added as a
1:1 ratio mixture at a total pressure of 250 psi followed by the
carbon dioxide (4.75 g for the emulsion and comparison run and 9.05
g for the microemulsion and comparison run). The cells were heated
to 80.degree. C. by the use of heating tape connected to a
temperature controller, and pressurized at 4000 psi by adding
carbon dioxide to the back sides of the respective pistons. Once
the desired temperature and pressure were achieved inside the cells
and the micellar system had formed by stirring and pumping,
1-decene (100 microliters) was injected via the sample loops on the
6-port valve of each cell, initiating the reactions. Samples were
taken from the two side-by-side cells after 1.45 hours for the
first side-by-side runs including an emulsion system and after 6
hours for the second side-by-side runs including a microemulsion
system. The samples were analyzed for percent conversion of the
1-decene, selectivity of conversion to the aldehydes, and the
straight to branched ratio of product.
[0081] As can be seen in Table 1, the formation of a micellar
solution significantly increases the reaction rate and yields; both
in the case of emulsion and microemulsion, as compared to a
two-phase system. The results are better than previously published
data in a two-phase biphasic system and comparable to data obtained
by Monflier et al., Angew. Chem. Int. Ed. Engl., vol. 34, pp.
2269-2271 (1995) for addition of, e.g., cyclodextrins, which behave
as an inverse phase transfer catalyst. After the reaction was
completed decreasing the temperature and pressure broke the
micellar solution. .sup.31P NMR of the remaining aqueous phase
showed that most of the catalyst was still intact although some
oxidized phosphine ligands were present.
1TABLE 1 (Hydroformylation of 1-decene.sup.a) Biphasic wt % wt %
Reaction Time mol % Conv. Sel..sup.e ratio System H.sub.2O Ligand
H.sub.2O (hours) catalyst.sup.d (%) (%) n/i.sup.f Two-phase 50
tppds 50 1.45 2.4 63 78 1.9 Emulsion.sup.b 50 tppds 50 1.45 2.4 85
94 1.4 Emulsion.sup.b 50 BINAS 50 4.0 2.0 >99 95 1.4 Two-phase
1.1 tppds 1.1 6.0 hours 4.0 58 53 2.3 Microemulsion.sup.c 1.1 tppds
1.1 6.0 hours 4.0 80 39 1.9 .sup.aReaction conditions: 80.degree.
C., 4000 psi. .sup.bUsing PBO-PEO. .sup.cUsing PFPE. .sup.dMole
percent catalyst to 1-decene. .sup.eSelectivity to aldehydes.
.sup.fRatio of linear to branched aldehyde.
EXAMPLE 2
[0082] Hydrogenation reactions were performed as follows: Under a
nitrogen atmosphere, two cells were loaded from the front end with
the selected surfactant (0.5 weight percent SAM-185 based on total
weight of water and carbon dioxide or no surfactant in the case of
the two-phase comparison run performed side-by-side with the
surfactant-containing system), water (4.75 g), catalyst
(RhCl(tppds).sub.3) and an internal standard of nonane. The cells
were sealed, removed from the nitrogen atmosphere and connected to
the pump and gas lines. The hydrogen was then added (250 psi)
followed by the carbon dioxide (4.75 g). The cells were heated to
40.degree. C. by heating tape connected to a temperature
controller, and pressurized at 4000 psi by adding carbon dioxide to
the back sides of the respective pistons. Once the desired
temperature and pressure were achieved inside the cells and the
micellar system had formed by stirring and pumping, the reactant,
either styrene or 1-decene, was injected via the sample loops on
the 6-port valve of each cell, initiating the reactions. Samples
were taken from the two side-by-side cells after 1.45 hours for the
first side-by-side runs including an emulsion system and at 6 hours
for the second side-by-side runs including a microemulsion system.
The samples were analyzed for percent hydrogenation of the styrene
and the 1-decene.
[0083] The results for hydrogenation of styrene (shown by equation
(6)) and 1-decene (shown by equation (7)) in a two phase versus
emulsion system are shown in Table 2. For both substrates the
yields were significantly higher in the emulsion system. 16
[0084] In the case of performing asymmetric hydrogenations, the
only difference would be the use of a chiral ligand and the same
results should be obtained.
2TABLE 2 (Hydrogenation reaction.sup.a) wt % Reaction mol % % yield
% yield Substrate H.sub.2O Time catalyst.sup.b Two-phase
Emulsion.sup.c Styrene 50 6 hours 6 22 69 1-decene 50 3 hours 1.6
10 32 .sup.aReaction conditions: 40.degree. C., 4000 psi.
.sup.bMole percent catalyst to substrate. .sup.cUsing PBO-PEO.
EXAMPLE 3
[0085] Hydrogenation reactions in both dense phase (T=28.degree.
C.) and supercritical (T=40.degree. C.) carbon dioxide and water
emulsions were performed using both nonionic (SAM-185) and cationic
(Lodyne S-106A) surfactants. The reactions were performed as in
example 2 with the only difference being the amount of surfactant,
catalyst and temperature used (see Table 3). Samples were taken
after 9 hours from each cell for analysis by gas chromatography
(GC). Greater yields of ethyl benzene were obtained using a
nonionic surfactant for this particular reaction system, and a
higher temperature was also an advantage. In the case of the
cationic surfactant the temperature effect was not as
noticeable.
3TABLE 3 Hydrogenation of Styrene in CO.sub.2/H.sub.2O
Emulsions.sup.a Surfactant T (.degree. C.) CO.sub.2-phase Yield
SAM-185 (nonionic) 28 Dense phase 59% SAM-185 40 Supercritical 68%
Lodyne 106A (cationic) 28 Dense phase 23% Lodyne 106A 40
Supercritical 20% .sup.aReaction conditions:, 1 mol % catalyst to
substrate, 50 wt % water, 3 wt % surfactant, 4000 psi, 9 h reaction
time.
EXAMPLE 4
[0086] Hydrogenation of Styrene:
[0087] The time profile (formation of product ethyl benzene) for
the hydrogenation of styrene is illustrated in FIG. 3 for the three
surfactants as well as control experiments run in two-phase
water/CO.sub.2 and water/toluene systems without added surfactants.
Control experiments reveal that the two-phase water/CO.sub.2 system
is more reactive than the water/toluene system. These results are
likely due to higher hydrogen solubility in the CO.sub.2 system and
potentially also to the lower interfacial tension between water and
CO.sub.2 as compared to water and traditional organic solvents.
While simple solvent replacement of toluene with carbon dioxide
leads to some rate enhancement in the present invention, it is
clear that this activity is still not practical for most nonpolar,
nonvolatile substrates. As shown in FIG. 3, the reaction rate for
styrene hydrogenation increases significantly upon addition of
surfactant and emulsion formation. The time profiles in FIG. 3
suggest the reaction is zero order in substrate throughout the
reaction for toluene/water and CO.sub.2/water and nearly zero order
for at least the first half of the reaction for the emulsions. The
initial catalytic activity can be quantified in terms of turnover
frequency (TOF), here defined as the mole of substrate transformed
per mole of catalyst per hour at 50% conversion. For styrene (FIG.
4) the TOF was found to be 4 h.sup.-1 in toluene/water, 26 h.sup.-1
CO.sub.2/water, and 150-300h.sup.-1 for the emulsions formed from
three different surfactants.
EXAMPLE 5
[0088] Pressure Effect of the Hydrogenation of Styrene and
1-Decene:
[0089] Reaction conditions were as in Example 2 except as noted.
Using 80 mM of the substrate and 1 mol % of the catalyst
RhCl(tppds).sub.3 (Rh/L=1/6) in a 50 weight percent water to
CO.sub.2 emulsion with 2 weight percent of the PBO-PEO surfactant.
T=40.degree. C. and P=4000 psi.
4TABLE 4 (Pressure Effect on Hydrogenation reaction.sup.a) wt %
Reaction mol % psi % yield Substrate H.sub.2O Time catalyst.sup.b
hydrogen Emulsion.sup.c Styrene 50 20 minutes 1 300 45 " 50 40
minutes 1 300 65 " 50 60 minutes 1 300 80 " 50 100 minutes 1 300 85
" 50 20 minutes 1 600 65 " 50 40 minutes 1 600 95 " 50 60 minutes 1
600 98 " 50 100 minutes 1 600 98 1-Decene 50 200 minutes 1 300 60 "
50 400 minutes 1 300 75 " 50 200 minutes 1 600 95 " 50 400 minutes
1 600 98 .sup.aReaction conditions: 40.degree. C., 4000 psi on
cell. .sup.bMole percent catalyst to substrate. .sup.cUsing
PBO-PEO.
EXAMPLE 6
[0090] Hydrogenation of Long Chained Olefins:
[0091] In an effort to ascertain whether the reaction was occurring
in the water phase or at the interface, a series of hydrophobic
1-alkenes was examined. The TOF at 50% conversion for 1-octene,
1-decene and 1-eicosene was measured to be 140 h.sup.-1, 110
h.sup.-1 and 30 h-.sup.-1, respectively. If the initial zero order
kinetic dependence on substrate concentration arises from a steady
state concentration of substrate in the aqueous phase (i.e., the
water solubility of the substrate), the relative rates would be
expected to correlate with the relative solubility in water for
these olefins, since the homogeneous reaction rate is known to be
independent of chain length. The solubility of 1-octene in water at
25.degree. C. is 2.7 mg/L water, and the solubility of higher
olefins decreases exponentially with molar volume. The observation
that 1-eicosene is only about four times slower than 1-octene,
despite its markedly lower (orders of magnitude) water solubility
indicates that the reaction could be occurring at the interface
where the relative concentrations may be much closer, rather than
in bulk water.
[0092] The reaction conditions were as follows. Using 80 mM of the
substrate and 1 mol % of the catalyst RhCl(tppds).sub.3 (Rh/L=1/6)
in a 50 weight percent water to CO.sub.2 emulsions with 2 weight
percent of the PBO-PEO surfactant. T=40.degree. C. and P=4000
psi.
EXAMPLE 7
[0093] Recycle Data For the Hydrogenation of Styrene:
[0094] After performing a hydrogenation reaction of styrene as in
example 5 the emulsion was broken by decreasing the pressure to
1200 psi and stopping the stirring and pump. Catalyst recycle was
demonstrated by transferring the product containing CO.sub.2 phase
under pressure to a separate high pressure reactor and then
charging the aqueous phase, still containing the catalyst and
surfactant, with more H.sub.2, CO.sub.2 and alkene.
Repressurization and recirculation led to emulsion formation. For
styrene, it was found that the catalyst activity remains
essentially constant for at least three cycles, i.e. complete
conversion after 3 h for cycle 1, 2 and 3 respectively,
demonstrating efficient catalyst recycle.
EXAMPLE 8
[0095] Oxidation of 2-octanol was performed as follows. Pairs of
cells were loaded from the front end with 5 mL water, 5 mL 30%
H.sub.2O.sub.2, 14 mg Na.sub.2WO.sub.4, 14 mg methyl
3-tri-n-octylammonium sulfate, and 150 .mu.l decane (used as
internal standard). To one of the cells 194 mg SAM-185 was also
added. Both cells were closed, connected to the pump, and 9.9 mL
CO.sub.2 was added. The cells were heated to 90.degree. C. by
heating tape connected to a temperature controller, and pressurized
to 4000 psi by adding carbon dioxide to the back sides of the
respective pistons. Once the desired temperature and pressure was
achieved inside the cell and an emulsions had formed in the one
containing the surfactant, 344 .mu.l 2-octanol was injected into
each cell through the 6-port valve. Samples taken from both cells
after 4 hours were analyzed by GC and showed total conversion to 2-
17
[0096] octanone for both reaction systems. The oxidation reaction
is shown below.
EXAMPLE 9
[0097] An example of hydrogenation in a biphasic reverse emulsion
with a carbon dioxide-soluble ligand was as follows. A carbon
dioxide-soluble catalyst complex was made by a ligand exchange of
tris[3,5-bis(trifluorom- ethyl)phenyl]phosphine with
chloro(1,5-cyclooctadiene) rhodium(I) dimer. Water soluble
substrates used as examples for hydrogenations in biphasic reverse
emulsions included methyl-2-acetamidoacryl ate and 2-acetamido
acrylic acid. Both were hydrogenated using of the carbon
dioixde-soluble
RhCl[tris(3,5-bis(trifluoromethyl)phenyl)phosphine].sub.2.
[0098] Reaction conditions were 80 mM substrate, 1 mol % catalyst,
50 weight percent H.sub.2O to CO.sub.2, 2.0 weight percent PBO-PEO
surfactant to the total amount of H.sub.2O and CO.sub.2, 40.degree.
C., 4000 psi. 18
[0099] Methyl-2-acetamidoacrylate was hydrogenated to complete
conversion in 1 hour and 2-acetamido acrylic acid to 75 percent
yield in 12 hours.
[0100] The present results of the examples demonstrate the benefits
of the present invention wherein catalyst utilization and recovery
brings the advantages of both heterogeneous and homogeneous
catalysis. Reactions occur in a homogeneous fluid with enhanced
diffusion, gas miscibility, and ability to control selectivity and
activity through ligand environment, solvent properties and choice
of surfactant. Valuable catalysts can be recovered and reused,
opening up a wide range of expensive catalysts for practical
commercial use, especially for the synthesis of specialty
chemicals. The process of the present invention should help
overcome major economic and environmental challenges to catalysis
science and industrial practice. It should also produce significant
economic and environmental benefit by reducing the use of hazardous
solvents, improving the recovery of expensive and possibly toxic
catalysts, minimizing waste generation and increasing energy
utilization through efficient separation of products, and
decreasing capital investments through the reduction in the number
of unit operations needed for product synthesis and
purification.
[0101] Although the present invention has been described with
reference to specific details, it is not intended that such details
should be regarded as limitations upon the scope of the invention,
except as and to the extent that they are included in the
accompanying claims.
* * * * *