U.S. patent application number 12/494098 was filed with the patent office on 2009-12-31 for compositions for carboxylic acid production and methods for making and using same.
This patent application is currently assigned to PRETIUM VENTURES AA, LLC. Invention is credited to Ronnie M. Hanes, Peter P. Hanik, James A. Hinnenkamp.
Application Number | 20090326268 12/494098 |
Document ID | / |
Family ID | 41445394 |
Filed Date | 2009-12-31 |
United States Patent
Application |
20090326268 |
Kind Code |
A1 |
Hanes; Ronnie M. ; et
al. |
December 31, 2009 |
COMPOSITIONS FOR CARBOXYLIC ACID PRODUCTION AND METHODS FOR MAKING
AND USING SAME
Abstract
An alcohol such as methanol is reacted with carbon monoxide in a
liquid reaction medium including a catalyst, an alkyl iodide such
as methyl iodide, alkyl acetate such as methyl acetate in specified
proportions, an additive, and an effective amount of water, where
the additive increases an ionic character of the hydrogen iodide
bond and the effective amount of water is sufficient to facilitate
carboxylic acid release after carbonylation at the catalyst and to
reduce anhydride formation. The present reaction system not only
provides an acid product at water levels considerable below levels
currently used, but also provides unexpected reaction rates and
unexpected high catalyst stability.
Inventors: |
Hanes; Ronnie M.; (Union
Grove, AL) ; Hanik; Peter P.; (Friendswood, TX)
; Hinnenkamp; James A.; (Cincinnati, OH) |
Correspondence
Address: |
ROBERT W STROZIER, P.L.L.C
PO BOX 429
BELLAIRE
TX
77402-0429
US
|
Assignee: |
PRETIUM VENTURES AA, LLC
Houston
TX
|
Family ID: |
41445394 |
Appl. No.: |
12/494098 |
Filed: |
June 29, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61133398 |
Jun 28, 2008 |
|
|
|
Current U.S.
Class: |
562/519 ;
252/183.11; 422/211 |
Current CPC
Class: |
B01J 8/00 20130101; B01J
2219/00006 20130101; C07C 51/12 20130101; B01J 31/20 20130101; C07C
51/50 20130101; C07C 2523/46 20130101; C07C 51/12 20130101; C07C
53/08 20130101; B01J 2531/822 20130101; B01J 2531/827 20130101;
B01J 2231/321 20130101 |
Class at
Publication: |
562/519 ;
252/183.11; 422/211 |
International
Class: |
C07C 51/12 20060101
C07C051/12; C09K 3/00 20060101 C09K003/00; B01J 8/00 20060101
B01J008/00 |
Claims
1. A carbonylation composition comprising: a metal-containing
catalyst, an alcohol (ROH) or an alkyl acetate (AcOR), an alkyl
iodide (RI), one or a plurality of hydrogen iodide (HI) solvating
additives, an effective amount of added water, and carbon monoxide,
where the catalyst converts the alcohol into a carboxylic acid
having one more carbon atom, the solvating additive increases an
ionic character of the hydrogen iodide bond of hydrogen iodide
formed during carbonylation reducing the effective amount of added
water to a concentration at or below 4 wt. % and improves catalyst
stability and where the effective amount of water is sufficient to
facilitate the release of carboxylic acid after carbonylation of
the alcohol/alkyl acetate and to reduce anhydride formation.
2. The composition of claim 1, wherein the R group of the ROH or
AcOR and RI is a linear alkyl group having between 1 and 6 carbon
atoms.
3. The composition of claim 1, wherein the solvating additive is
selected from the group consisting of (1) polyols
(R.sup.1(OH).sub.n), compounds including two or more hydroxy
groups, (2) poly carboxylic acids (R.sup.2(COOH).sub.n), compounds
including two or more carboxylic acid groups, (3) sulfones
(R.sup.3SO.sub.2R.sup.4), (4) oligomers, co-oligomers, polymers and
co-polymers including at least one hydroxy containing monomer
(poly(OH)), (5) oligomers, co-oligomers, polymers and co-polymers
including at least one carboxylic acid containing monomer
(poly(COOH)), (6) oligomers, co-oligomers, polymers and co-polymers
including at least one sulfone containing monomer (poly(SO.sub.2)),
and (7) mixtures thereof.
4. The composition of claim 3, wherein the solvating additive has a
boiling point or vaporization temperature at least 10.degree. C.
above a temperature of the product carboxylic acid.
5. The composition of claim 3, wherein the solvating additive
comprises a polyol having the formula R.sup.1(OH).sub.n, where
R.sup.1 is selected from the group consisting of and n is an
integer having a value between 1 and a maximum number replaceable
hydrogen atoms and mixtures thereof.
6. The composition of claim 3, wherein the solvating additive
comprises poly carboxylic acids (R.sup.2(COOH).sub.n), compounds
including two or more carboxylic acid groups, and mixtures
thereof
7. The composition of claim 3, wherein the solvating additive
comprises sulfones (R.sup.3SO.sub.2R.sup.4) and mixtures
thereof.
8. The composition of claim 3, wherein the solvating additive
comprises oligomers, co-oligomers, polymers and co-polymers
including at least one hydroxy containing monomer (poly(OH)), and
mixtures thereof
9. The composition of claim 3, wherein the solvating additive
comprises oligomers, co-oligomers, polymers and co-polymers
including at least one carboxylic acid containing monomer
(poly(COOH)), and mixtures thereof
10. The composition of claim 3, wherein the solvating additive
comprises oligomers, co-oligomers, polymers and co-polymers
including at least one sulfone containing monomer (poly(SO.sub.2)),
and mixtures thereof.
11. The composition of claim 1, wherein the catalyst is present in
an amount sufficient to achieve a desired carbonylation reaction
rate.
12. The composition of claim 1, wherein the catalyst is present in
an amount between about 200 and about 1200 ppm (about
2.times.10.sup.-3 to about 13.times.10.sup.-3 M).
13. The composition of claim 1, wherein the catalyst is present in
an amount between about 400 to about 1000 ppm (about
4.times.10.sup.-3 to about 10.times.10.sup.-3 M).
14. The composition of claim 1, wherein the metal-containing
catalyst is selected from the group consisting of rhodium based
catalysts, iridium based catalysts, palladium based catalysts, or
mixtures thereof.
15. The composition of claim 14, wherein the metal-containing
catalyst comprises a rhodium based catalyst.
16. The composition of claim 15, wherein the metal-containing
catalyst comprises rhodium metal, rhodium salts, rhodium oxides,
rhodium acetates, organo-rhodium compounds, coordination compounds
of rhodium, or mixtures or combinations thereof.
17. The composition of claim 16, wherein the metal-containing
catalyst comprises a rhodium-containing compound selected from the
group consisting of RhCl.sub.3; RhBr.sub.3; RhI.sub.3;
RhCl.sub.3.3H.sub.2O; RhBr.sub.3.3H.sub.2O; RhI.sub.3.3H.sub.2O;
Rh.sub.2(CO).sub.4Cl.sub.2; Rh.sub.2(CO).sub.4Br.sub.2;
Rh.sub.2(CO).sub.4I.sub.2; Rh.sub.2(CO).sub.8;
Rh(CH.sub.3CO.sub.2).sub.2; Rh(CH.sub.3CO.sub.2).sub.3;
Rh[(C.sub.6H.sub.5).sub.3P].sub.2(CO)I;
Rh[(C.sub.6H.sub.5P)].sub.2(CO)Cl; Rh metal; Rh(NO.sub.3).sub.3;
Rh(SnCl.sub.3)[(C.sub.6H.sub.5).sub.3P].sub.2;
RhCl(CO)[(C.sub.6H.sub.5).sub.3As].sub.2;
RhI(CO)[(C.sub.6H.sub.5).sub.3Sb].sub.2; [Y][Rh(CO).sub.2X.sub.2],
where X is Cl.sup.-, Br.sup.- or I.sup.-; and Y is a cation
selected from the group consisting of positive ions from Group IA
of the Periodic Table of Elements, such as H, Li, Na, K, or Y is a
quaternary ion of N, As or P;
Rh[(C.sub.6H.sub.5).sub.3P].sub.2(CO)Br;
Rh[(n-C.sub.4H.sub.9).sub.3P].sub.2(CO)Br;
Rh[(n-C.sub.4H.sub.9).sub.3P].sub.2(CO)I;
RhBr[(C.sub.6H.sub.5).sub.3P].sub.3;
RhI[(C.sub.6H.sub.5).sub.3P].sub.3;
RhCl[(C.sub.6H.sub.5).sub.3P].sub.3;
RhCl[(C.sub.6H.sub.5).sub.3P].sub.3H.sub.2;
[(C.sub.6H.sub.5).sub.3P].sub.3Rh(CO)H; Rh.sub.2O.sub.3;
[Rh(C.sub.3H.sub.4).sub.2Cl].sub.2;
K.sub.4Rh.sub.2Cl.sub.2(SnCl.sub.2).sub.4;
K.sub.4Rh.sub.2Br.sub.2(SnBr.sub.3).sub.4;
[H][Rh(CO).sub.2I.sub.2]; K.sub.4Rh.sub.2I.sub.2(SnI.sub.2).sub.4,
and the like and mixtures or combinations thereof.
18. The composition of claim 17, wherein the metal-containing
catalyst comprises a rhodium-containing compound selected from the
group consisting of Rh.sub.2(CO).sub.4I.sub.2,
Rh.sub.2(CO).sub.4Br.sub.2, Rh.sub.2(CO).sub.4Cl.sub.2,
Rh(CH.sub.3CO.sub.2).sub.2, Rh(CH.sub.3CO.sub.2).sub.3,
[H][Rh(CO).sub.2I.sub.2] or mixtures or combinations thereof.
19. The composition of claim 18, wherein the metal-containing
catalyst comprises a rhodium-containing compound selected from the
group consisting of [H][Rh(CO).sub.2I.sub.2],
Rh(CH.sub.3CO.sub.2).sub.2, Rh(CH.sub.3CO.sub.2).sub.3 or mixtures
or combinations thereof.
20. The composition of claim 14, wherein the metal-containing
catalyst comprises an iridium based catalyst.
21. The composition of claim 20, wherein an iridium-containing
compound selected from the group consisting of IrCl.sub.3,
IrI.sub.3, IrBr.sub.3, [Ir(CO).sub.2I].sub.2,
[Ir(CO).sub.2Cl].sub.2, [Ir(CO).sub.2Br].sub.2,
[Ir(CO).sub.4I.sub.2].sup.-H.sup.+, [Ir(CO).sub.2].sup.-H.sup.+,
[Ir(CO).sup.2I.sub.2].sup.-H.sup.+,
[Ir(CH.sub.3)I.sub.3(CO).sub.2].sup.-H.sup.+, Ir.sub.4(CO).sub.12,
IrCl.sub.3.4H.sub.2O, IrBr.sub.3.4H.sub.2O, Ir.sub.3(CO).sub.12,
Ir.sub.2O.sub.3, IrO.sub.2, Ir(acac)(CO).sub.2, Ir(acac).sub.3,
Ir(Ac).sub.3, [Ir.sub.3O(OAc).sub.6(H.sub.2O).sub.3][OAc], and
H.sub.2[IrCl.sub.6].
22. The composition of claim 21, wherein an iridium-containing
compound selected from the group consisting of acetates, oxalates,
acetoacetates, and mixtures thereof.
23. The composition of claim 1, wherein the iridium-based catalyst
includes a co-catalyst including metals and metal compounds
selected from the group consisting of osmium, rhenium, ruthenium,
cadmium, mercury, zinc, gallium, indium, and tungsten, their
compounds, and mixtures thereof.
24. A system for producing carboxylic acids comprising: a reaction
subsystem including at least one reactor vessel charged with a
liquid reaction media comprising: a metal-containing catalyst, an
alcohol (ROH) forming a corresponding alkyl acetate (AcOR) in situ,
an alkyl iodide (RI), one or a plurality of hydrogen iodide (HI)
solvating additives, an effective amount of added water, and an
effective amount of added water; a carbon monoxide supply subsystem
for supplying carbon monoxide to the at least one reactor vessel,
and a carboxylic acid purification and recycle subsystem for
purifying the carboxylic acid product and recycling recovered alkyl
acetate, alcohol, and alkyl iodide to the at least on reactor
vessel, where the catalyst converts the alcohol into a carboxylic
acid having one more carbon atom, the solvating additive increases
an ionic character of the hydrogen iodide bond of hydrogen iodide
formed during carbonylation reducing the effective amount of added
water to a concentration at or below 4 wt. % and improves catalyst
stability and where the effective amount of water is sufficient to
facilitate the release of carboxylic acid after carbonylation of
the alcohol/alkyl acetate and to reduce anhydride formation.
25. A method for producing carboxylic acids comprising: charging a
reactor vessel with a liquid reaction media comprising: a
metal-containing catalyst, an alcohol (ROH) forming a corresponding
alkyl acetate (AcOR) upon addition to the reaction media, an alkyl
iodide (RI), one or a plurality of hydrogen iodide (HI) solvating
additives, an effective amount of added water, and supplying carbon
monoxide to the reaction vessel; removing the media or a portion
thereof, separating the low boiling components including the
carboxylic acid to form a crude carboxylic acid product and,
recycling the high boiling components back to the reactor vessel;
separating the low boiling components from the crude acid product
to form a purified carboxylic acid product, and returning other low
boiling components to the reactor vessel, where the catalyst
converts the alcohol into a carboxylic acid having one more carbon
atom, the solvating additive increases an ionic character of the
hydrogen iodide bond of hydrogen iodide formed during carbonylation
reducing the effective amount of added water to a concentration at
or below 4 wt. % and improves catalyst stability and where the
effective amount of water is sufficient to facilitate the release
of carboxylic acid after carbonylation of the alcohol/alkyl acetate
and to reduce anhydride formation.
Description
RELATED APPLICATIONS
[0001] This application claims priority to and the benefit of U.S.
Provisional Patent Application Ser. No. 61/133,398, filed Jun. 28,
2008.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the present invention relate to a composition
for carboxylic acid production and methods for making and using
same.
[0004] More particularly, embodiments of the present invention
relate to a composition for carboxylic acid production and methods
for making and using same, where the composition includes a metal
catalyst, carbon monoxide, an alkanol, an iodine source, an
additive providing hydrogen bonding to HI present in the reaction
media, and optionally added water.
[0005] 2. Description of the Related Art
[0006] Production of acetic acid via methanol carbonylation is an
industrial process used on a global basis to produce billions of
pounds of glacial acetic acid. The process as currently practiced
commercially operates under relatively mild conditions with high
selectivity for utilization of methanol and carbon monoxide raw
materials.
[0007] A large body of literature pertaining to this process exists
and a review of this literature indicates several key operating
parameters that must be considered for efficient process operation.
One of these parameters concerns maintaining a low concentration of
water in the reactor. This requirement is obvious; glacial acetic
acid is marketed with a water concentration in the parts per
million range. Thus, reactor water above ppm levels must be
removed, requiring energy--the more water, the higher the energy
requirement.
[0008] Those skilled in the art are familiar with the original
literature by Monsanto (see, e.g., U.S. Pat. No. 3,769,329,
inventor of the basic modern process) and a reading of this
literature indicates a second parameter concerning catalyst
stability. Catalyst stability is adversely affected by lower
reactor water concentrations. Moreover, increasing water increases
by-product formation due to such reactions as the water gas shift
reaction, which is directly proportional to the reactor water
concentration.
[0009] Another problem with the current processes is that catalyst
stability and activity is lower than desired even with high reactor
water concentrations. The literature indicates that oxidative
addition of hydrogen iodide to the active rhodium species is the
first step in a series of reactions leading to both the undesired
water gas shift reaction and to rhodium precipitation. See, e.g.,
N. Hallinan and J. Hinnenkamp, Rhodium Catalyzed Methanol
Carbonylation: New Low Water Technology, Proceedings of the Organic
Reactions Catalysis Society, 2000. The reference disclosed one can
inhibit the addition of hydrogen iodide to the rhodium species
through the interaction of HI with a weak base such as a tertiary
phosphine oxide. The reference further disclosed that if too strong
a base is used, the hydrogen iodide intermediate is removed from
the iodide cycle such that methyl iodide is not regenerated from
methyl acetate and the reaction rate drops significantly and even
stops. Thus, selection of an additive with a base strength within a
very narrow range is effective in maintaining the rhodium in the
desired active and stable form independent of reactor water
concentration.
[0010] Thus, there is a need in the art for an improved carboxylic
acid preparation process. The new processes and catalyst
compositions provide a means to provide improved catalyst
stability, reduced energy consumption, and reduced by-product
formation. Because the catalyst metals used in this process are
expensive (e.g., Rh, Ir, Pd, etc.), improving catalyst stability
and simplifying acetic acid recovery can decrease metal loss and
reduce catalyst regeneration.
SUMMARY OF THE INVENTION
[0011] Embodiments of the present invention relate to liquid
reaction media for carbonylation of alcohols to carboxylic acids,
where the media include a catalyst, an alcohol (ROH) or alcohol
equivalents such as an alkyl acetate (AcOR), a source of iodide to
form an alkyl iodide (RI), an effective amount of an additive, and
optionally an effective amount of added water in the presence of
carbon monoxide, where the media converts the alcohol to a
carboxylic acid having one more carbon atom, the effective amount
of the additive is sufficient to increase an ionic character of the
hydrogen iodide bond produced during the carbonylation reaction, to
reduce added water below levels currently used or eliminate added
water and to improve catalyst stability and where the effective
amount of added water is sufficient to facilitate carboxylic acid
formation after carbonylation of the alcohol at the catalyst and to
reduce anhydride formation.
[0012] Embodiments of the present invention relate to systems for
producing carboxylic acids, including a reaction subsystem
including at least one reactor vessel charged with a liquid
reaction media of this invention, reactant sources, feed lines from
the reactant sources to the reactor, a separation subsystem for
separating the product carboxylic acid from the media and a recycle
subsystem of recycling the media to the reaction subsystem.
[0013] Embodiments of the present invention relate to methods for
producing carboxylic acids, including charging a reactor vessel
with a liquid reaction media of this invention. Once the media is
charged, supplying carbon monoxide to the reaction vessel. After
reaction or on a continuous or semi-continuous basis, removing the
media or a portion thereof. After removing the media or a portion
thereof, separating the low boiling components including the
carboxylic acid and recycling the high boiling components back to
the reactor vessel. After separating the low boiling components,
purifying the carboxylic acid and returning other low boiling
components to the reactor vessel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The invention can be better understood with reference to the
following detailed description together with the appended
illustrative drawings in which like elements are numbered the
same:
[0015] FIG. 1 depicts a graph of initial Rh(I) concentrations and
Rh(I) concentration after 20 minutes of reaction for various
additives of this invention relative to a 14 wt. % water and a 2
wt. % water controls.
[0016] FIG. 2 depicts a graph of moles of acetic acid produced,
moles of methyl propanoate consumed, and moles of methyl iodide
consumed for various additives of this invention relative to a 14
wt. % water and a 2 wt. % water controls.
[0017] FIG. 3 depicts a graph of moles of carbon monoxide consumed
for various additives of this invention relative to a 14 wt. %
water and a 2 wt. % water controls.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The inventors have found that new catalytic compositions and
methods for using these compositions to prepare carboxylic acids
via carbonylation of an alcohol or alcohol equivalent can be
formulated and implemented. The inventors have found that catalyst
activity and stability can be improved through the addition of one
additive or a plurality of additives, which increase an ionic
character of the bond of hydrogen iodide (HI) formed during the
carbonylation reaction. The literature supports a mechanism for
producing a carboxylic acid (RCOOH) such as acetic acid (AcOH). The
mechanism is thought to include an oxidative addition of an alkyl
iodide (RI) such as methyl iodide (MeI) to a metal catalytic
species such as a rhodium and/or iridium and/or palladium catalytic
species to form a pre-carbonylation intermediate. The mechanism is
also thought to support a similar mechanism for by-product
production and catalyst precipitation that starts with an oxidative
addition of hydrogen iodide (HI) to the metal catalytic species
instead of the alkyl iodide. The addition of HI is thought to be
the first step in the water gas shift reaction (a by-product
reaction) and the first step in a reaction that leads to catalyst
precipitation. It is known that hydrogen iodide (HI) has the unique
capability of exhibiting either covalent bonding or ionic bonding,
while the methyl (alkyl) iodide (MeI (RI)) possesses only covalent
bond character. While not meaning to be bound to any particular
theory, the inventors have inferred from the action of the weak
base in the Hallinan and Hinnenkamp reference discussed above, that
the oxidative addition of HI to the metal catalytic species occurs
when HI is in a covalently bonded state, the HI bond is covalent,
not ionic. Moreover, the inventors have further inferred that the
reaction between methyl (alkyl)acetate and HI to regenerate the
methyl (alkyl) iodide occurs when hydrogen iodide is in an
ionically bonded state, the HI bond is ionic, not covalent. This
latter reaction, the regeneration of MeI, is necessary for the
reaction to continue.
[0019] The inventors have also found that by adding one additive or
a plurality of additives to active media, an amount of HI in its
covalently bonded state can be reduced, while increasing an amount
of HI in its ionically bonded state. The term "active media" means
the liquid reaction media that carbonylates an alkanol equivalent
(an acetate), via its iodide, to a carboxylic acid having one
additional carbon atom. In certain embodiments, the amount of HI in
its covalently bonded state can be substantially eliminated
resulting in substantially all of the HI being in its ionically
bonded state. The inventors have found that these additives are
capable of reducing the amount of covalently bonded HI to
substantially eliminating the amount of covalently bonded HI. The
additives can be used to optimize an amount of ionically bonded HI.
In certain embodiments, the additives can be used to maximize the
amount of ionically bonded HI in the active media. By maintaining
the HI entirely or substantially entirely in its ionically bonded
state, by-product production and catalyst precipitation and/or
deactivation through oxidation addition of HI to the metal
catalytic species can be minimized and the rate of methyl (alkyl)
iodide regeneration can be increased increasing its steady state
concentration. The inventors further believe that these
observations explain the rate and stability dependence of the
active media on water observed in the original process, because
water will hydrogen bond with hydrogen iodide increasing an ionic
character of the HI bond. The term "substantially" as used here
means that at least 85% of the HI present in the active media is in
its ionically bonded state. In other embodiments, the term
"substantially" means that at least 90% of the HI present in the
active media is in its ionically bonded state. In other
embodiments, the term "substantially" means that at least 95% of
the HI present in the active media is in its ionically bonded
state. In other embodiments, the term "substantially" means that at
least 99% of the HI present in the active media is in its ionically
bonded state.
[0020] The inventors have applied these inferences to construct
novel active media to increase catalyst activity and stability,
while allowing added reactor water to be reduced and/or minimized
to that needed for the reaction to proceed or to that cyclically
produced and consumed in the reaction, one water molecule produced
to form the acetate and one water molecule consumed to form the
carboxylic acid from the carbonylation intermediate, Cat-CO-Me. The
novel active media includes the addition of stabilizing agents
adapted to interact with HI to increase its ionic bond character
increasing the amount of ionically bonded HI, reducing the amount
of covalently bonded HI, reducing by-product formation and reducing
catalyst precipitation.
[0021] In the production of acetic acid from methanol
carbonylation, methanol is fed to the reactor vessel where it
immediately reacts with acetic acid to form methyl acetate and
water. Methyl acetate, thus, formed then reacts with HI to form
methyl iodide and acetic acid. The addition of methyl iodide to the
active catalyst is the rate limiting step in the carbonylation
reaction. Therefore, as water is liberated in the formation of
methyl acetate from methanol and acetic acid, it is immediately
consumed in the liberation of acetic acid from the carbonylated
methylated catalyst (RhCOMe). The steady state water concentration
maintained in the reaction is used to facilitate conversion of
acetic anhydride back to acetic acid. The present invention is to
add additives to reduce added water to a concentration less than 2
wt. %. Embodiments of this invention, the water concentration is
less than 1 wt. %. Embodiments of this invention, the water
concentration is less than 0.5 wt. %.
[0022] Broadly, embodiments of the present invention relate to
active media including additives capable of increasing the ionic
bond character of HI in the active media.
[0023] Embodiments of the present invention also relate to active
media including a low vapor pressure additive or additives, where
the additive or additives are present in an amount or concentration
sufficient to maintain all or substantially all of the HI in its
ionically bonded state. These additives provide catalyst activity
and stability, while allowing reactor water concentration to be
significantly reduced.
[0024] Embodiments of the present invention relate to active media
including a low vapor pressure, ionic liquid or a plurality of
ionic liquids, where the ionic liquids are present in an amount or
concentration sufficient to maintain all or substantially all of
the HI in its ionically bonded state. These additives provide
catalyst activity and stability, while allowing reactor water
concentration to be significantly reduced.
[0025] An additional benefit of employing the novel concepts
detailed in this invention would be the possible simplification of
the production process. If a stable, active catalyst is provided
that permits a lower water concentration, potentially even
minimizing water to that needed to release the carboxylated MeI as
AcOH using low volatility additive under reaction conditions, then
the reaction can be carried out in a manner similar to a fixed bed
catalyst reactor. That is, the homogeneous catalyst and other
reaction components are contained in a reactor vessel from which
only product vapor streams are removed. In the current process,
liquid streams are removed from the reactor in order to remove the
acetic acid produced. With a stable catalyst and low volatility
components and water minimized to acetic acid release, reactor
conditions can be selected such that the acetic acid can be removed
from the reactor as a vapor stream at a production rate of acetic
acid under the reaction conditions. This would eliminate the flash
vessel and associated recycle equipment. Because the flash vessel
is a zone of low carbon monoxide concentration, which destabilizes
the rhodium catalyst, removal of this vessel would enhance catalyst
stability by removing a low carbon monoxide pressure zone.
Moreover, because the flash vessel and associated equipment is
constructed of exotic alloys due to the corrosive nature of the
process, a significant capital savings would be realized by
eliminating this equipment.
[0026] Although the kinetic rate constants for the
iridium-catalyzed methanol carbonylation processes are different in
some steps, the overall reaction mechanism is viewed to be very
similar for both rhodium-based and iridium-based processes. Thus,
it would be expected that application of the teachings of this
invention would have benefits in both the rhodium-based and
iridium-based processes for the production of acetic acid, though
only the rhodium-based system has been experimentally addressed
here. The application also envision the use of palladium-based
catalyst systems or mixed catalyst system.
Suitable Reagents and Reagent Ranges
[0027] The present invention can be practiced with the ingredients
and ranges set forth in Table 1, which lists reagents and
additives.
TABLE-US-00001 TABLE 1 Reagent Table Component Exemplary Examples
Ranges Catalyst Metals rhodium (Rh), iridium (Ir), palladium (Pd),
or mixtures or 100 ppm-1200 ppm combinations thereof Alcohol Source
alkyl acetate (AcOR) N/A Iodide Source alkyl iodide (RI) or alkyl
acetic (AcOR)/HI N/A Solvating Additives carboxylic acids,
sulfones, polyols, other weak acids, mixtures 0.1 M-3M thereof,
etc. Carboxylic Acids di-carboxylic acids, tri-carboxylic acids,
tetra- carboxylic acids, poly-carboxylic acids, oliogomers and
polymers containing carboxylic acid monomers such as acrylic acid,
methacrylic acid, maleic anhydride, etc., cooligomers and
copolymers containing a carboxylic acid monomer, etc. and mixtures
thereof Sulfones dialkyl sulfones (RSO.sub.2R'), diaryl sulfones
(ASO.sub.2A'), alky, aryl sulfones (RSO.sub.2A), sulfone oligomers,
polysulfones, sulfone cooligomers and copolymers, etc. and mixtures
thereof Polyols compounds including two or more hydroxy group
(R(OH).sub.n), vinyl alcohol oliogmers and polymers, vinyl alcohol
cooligomers and copolymers, etc. Weak Acids boric acid, boronic
acids, etc. Hydroxide Donors water added water 0 wt. % to wt. %
[0028] Although sulfolane, a cyclic alkenyl sulfone (five membered
ring), has been used as a solvent, which U.S. Pat. No. 5,817,869
disclosed as being inert in the reaction media. "The term `inert`
as used herein means that the solvent or diluent does not interfere
with the reaction to any significant extent." U.S. Pat. No.
5,817,869 at Col. 7, 11. 28-30. "Generally, the reaction is carried
[out] in the absence of any solvent or diluent other than those
required to introduce reactants or catalyst components into the
reactor." U.S. Pat. No. 5,817,869 at Col. 7, 11. 36-48. This
disclosure teaches away from the use of sulfones and the other
compounds set forth above designed to increase the ionic bond
character of the HI bond, thereby increasing catalyst stability by
reducing HI induced catalyst deactivation.
Additives
[0029] Suitable additives capable of increasing the ionic bond
character of HI include, without limitation: (1) polyols
(R.sup.1(OH).sub.n), compounds including two or more hydroxy
groups, where in n is an integer having a value between 2 and the
maximum number of hydroxy groups that can be accommodated based on
the number of carbon atoms in the R.sup.1 group, (2) poly
carboxylic acids (R.sup.2(COOH).sub.n), compounds including two or
more carboxylic acid groups, where in n is an integer having a
value between 2 and the maximum number of carboxylic groups that
can be accommodated based on the number of carbon atoms in the
R.sup.2 group, (3) sulfones (R.sup.3SO.sub.2R.sup.4), (4)
oligomers, co-oligomers, polymers and co-polymers including at
least one hydroxy containing monomer (poly(OH)), (5) oligomers,
co-oligomers, polymers and co-polymers including at least one
carboxylic acid containing monomer (poly(COOH)), (6) oligomers,
co-oligomers, polymers and co-polymers including at least one
sulfone containing monomer (poly(SO.sub.2)), (7) other compounds
capable of increasing the ionic character of the HI bond, and (8)
mixtures thereof. In certain embodiments, the additive(s) have a
boiling point or vaporization temperature at least 10.degree. C.
above a temperature of the product carboxylic acid. Such high
boiling additives would remain in a reactor/flash tank section of
the process simplifying the distillation section of the
process.
[0030] The R.sup.1, R.sup.2, R.sup.3, and R.sup.4 groups in the
above formulas are generally carbyl group including from about 1 to
about 20 carbon atoms. The groups can be alkyl, aryl, aralkyl,
alkaryl, or combinations thereof.
[0031] As employed herein, the alkyl groups, singly or in
combination with other groups, include between 1 to 20 carbon atoms
and may be linear, branched, or cyclic. Non-limiting exemplary
examples including methyl, ethyl, propyl, isopropyl, butyl,
isobutyl, t-butyl, amyl, pentyl, hexyl, octyl, cyclopropyl,
cyclobutyl, cyclopentyl, cyclohexyl, and the like. In certain
embodiments, the alkyl groups include between 1 to 8 carbon
atoms.
[0032] As employed herein, the aryl groups are aromatic ring
compounds including between from 6 to 18 carbon atoms. Non-limiting
exemplary examples including phenyl, benzyl, tolyl, xylyl,
.alpha.-naphthyl, .beta.-naphthyl, and the like. In certain
embodiments, the aryl group is phenyl.
[0033] As employed herein, the aralkyl groups, singly or in
combination with other groups, contain up to 16 carbon atoms with
each aryl group containing from 6 to 10 carbon atoms and each alkyl
group containing up to 6 carbon atoms which may be in the normal or
branched configuration. Preferably, each aryl group contains 6
carbon atoms and each alkyl group contains 1 to 3 carbon atoms.
[0034] As employed herein, the alkaryl groups, singly or in
combination with other groups, contain up to 16 carbon atoms with
each alkyl group containing up to 8 carbon atoms which may be in
the normal or branched configuration, and each aryl group
containing from 6 to 10 carbon atoms. Preferably, each alkyl group
contains 6 carbon atoms.
[0035] As indicated herein each R.sup.1, R.sup.2, R.sup.3, and
R.sup.4 group may be substituted or unsubstituted. When R.sup.1,
R.sup.2, R.sup.3, and/or R.sup.4 are substituted, it is typically
substituted with an alkyl group as defined herein above. R.sup.1,
R.sup.2, R.sup.3, and/or R.sup.4 may also be substituted with other
substituents such as halogen, hydroxy, nitro, amino and the
like.
[0036] In certain embodiments, from about 0.2 to about 3M (or about
0.3 wt. % to about 4 wt. %) of one additive or a plurality of
additives are present in the liquid reaction medium. In other
embodiments, from about 0.4 to about 1.5M (or about 0.6 wt. % to
about 2 wt. %) of one additive or a plurality of additives are
present in the liquid reaction medium.
Other Additives
[0037] Suitable secondary additives can include, without
limitations, alkali iodides such as lithium iodide (LiI), sodium
iodide (NaI), potassium iodide (KI), or the like or mixtures
thereof (see, e.g., U.S. Pat. Nos. 5,214,203; 5,391,821; 5,003,104;
5,001,259; 5,026,908; 5,144,068; 5,281,751 and 5,416,237),
pentavalent Group VA oxide of the formula: R.sub.3M=O, where M is
an element from Group VA of the Periodic Table of Elements, such as
N, P, As, Sb or Bi; and each R is independently a substituted or
unsubstituted alkyl, aryl, aralkyl or alkaryl wherein any of which
substituents of the carbon chains may be straight or branched or
both (see, e.g., U.S. Pat. No. 5,817,869), alkali and alkaline
metal fluorides (LiF, NaF, KF, MgF.sub.2, CaF.sub.2, etc.) or other
fluoride salts, metal sulfates, metal sulfites, or mixtures or
combinations thereof.
[0038] The pentavalent Group VA oxide is introduced into the
carbonylation system in an amount such that its concentration
relative to rhodium is greater than about 60:1. The practice of the
invention further comprises introducing water to the carbonylation
system at an amount of from about 0 wt. % to about 3 wt. % (which
corresponds to a molarity of water of from about 0 M to about 7.5M)
based on the total amount of the carbonylation system, inclusive of
the additives and other additives such as pentavalent Group VA
oxide(s). In other embodiments, the concentration of water is from
about 0.5 wt. to about 2 wt. %. In other embodiments, the
concentration is about 1 wt. % to about 2 wt. %. It should be
recognized that the water concentration can be higher for those
system including novel HI solvating additives of this
invention.
Solvents
[0039] Suitable solvents for use in the present invention include,
without limitation, alkyl carboxylic acids such as acetic acid,
propanoic acid, butanoic acid, or other linear carboxylic acids.
Other solvents well known the art can also be used such as dioxane,
sulfolane, or other such solvents.
Catalysts
[0040] Suitable catalyst for use in the present invention include,
without limitation, rhodium based catalysts, iridium based
catalysts, palladium based catalysts, or mixtures thereof. In
certain embodiments, the catalyst is a rhodium based catalyst. In
other embodiments, the catalyst is an iridium based catalyst.
[0041] Non-limiting exemplary examples of rhodium-based catalysts
for use in the present invention include those known and used in
the prior art for carbonylation purposes. In certain embodiments,
the rhodium-based catalysts are those used in the prior art
especially for the production of acetic acid via carbonylation.
[0042] The rhodium-based catalysts of this invention may be
introduced into the reaction zone as a suitable compound of rhodium
or of rhodium metal. Among the materials which may be charged into
the reaction zone in this regard are, without limitation, rhodium
metal, rhodium salts, rhodium oxides, rhodium acetates,
organo-rhodium compounds, coordination compounds of rhodium, and
the like or mixtures or combinations thereof.
[0043] Non-limiting specific examples of rhodium-containing
compounds that can serve as the rhodium source for the rhodium
based catalysts of this invention include RhCl.sub.3; RhBr.sub.3;
RhI.sub.3; RhCl.sub.3.3H.sub.2O; RhBr.sub.3.3H.sub.2O;
RhI.sub.3.3H.sub.2O; Rh.sub.2(CO).sub.4Cl.sub.2;
Rh.sub.2(CO).sub.4Br.sub.2; Rh.sub.2(CO).sub.4I.sub.2;
Rh.sub.2(CO).sub.8; Rh(CH.sub.3CO.sub.2).sub.2;
Rh(CH.sub.3CO.sub.2).sub.3; Rh[(C.sub.6H.sub.5).sub.3P].sub.2(CO)I;
Rh[(C.sub.6H.sub.5P)].sub.2(CO)Cl; Rh metal; Rh(NO.sub.3).sub.3;
Rh(SnCl.sub.3)[(C.sub.6H.sub.5).sub.3P].sub.2;
RhCl(CO)[(C.sub.6H.sub.5).sub.3As].sub.2;
RhI(CO)[(C.sub.6H.sub.5).sub.3Sb].sub.2; [Y][Rh(CO).sub.2X.sub.2],
where X is Cl.sup.-, Br.sup.- or I.sup.-; and Y is a cation
selected from the group consisting of positive ions from Group IA
of the Periodic Table of Elements, such as H, Li, Na, K, or Y is a
quaternary ion of N, As or P;
Rh[(C.sub.6H.sub.5).sub.3P].sub.2(CO)Br;
Rh[(n-C.sub.4H.sub.9).sub.3P].sub.2(CO)Br;
Rh[(n-C.sub.4H.sub.9).sub.3P].sub.2(CO)I;
RhBr[(C.sub.6H.sub.5).sub.3P].sub.3;
RhI[(C.sub.6H.sub.5).sub.3P].sub.3;
RhCl[(C.sub.6H.sub.5).sub.3P].sub.3;
RhCl[(C.sub.6H.sub.5).sub.3P].sub.3H.sub.2;
[(C.sub.6H.sub.5).sub.3P].sub.3Rh(CO)H; Rh.sub.2O.sub.3;
[Rh(C.sub.3H.sub.4).sub.2Cl].sub.2;
K.sub.4Rh.sub.2Cl.sub.2(SnCl.sub.2).sub.4;
K.sub.4Rh.sub.2Br.sub.2(SnBr.sub.3).sub.4;
[H][Rh(CO).sub.2I.sub.2]; K.sub.4Rh.sub.2I.sub.2(SnI.sub.2).sub.4,
and the like and mixtures or combinations thereof.
[0044] In certain embodiments, rhodium-containing compounds that
can serve as the rhodium source for the rhodium based catalysts of
this invention include Rh.sub.2(CO).sub.4I.sub.2,
Rh.sub.2(CO).sub.4Br.sub.2, Rh.sub.2(CO).sub.4Cl.sub.2,
Rh(CH.sub.3CO.sub.2).sub.2, Rh(CH.sub.3CO.sub.2).sub.3,
[H][Rh(CO).sub.2I.sub.2] or mixtures or combinations thereof. In
other embodiments, rhodium-containing compounds that can serve as
the rhodium source for the rhodium based catalysts of this
invention include [H][Rh(CO).sub.2I.sub.2],
Rh(CH.sub.3CO.sub.2).sub.2, Rh(CH.sub.3CO.sub.2).sub.3 or mixtures
or combinations thereof.
[0045] In practice, the rhodium concentration can vary over a wide
range, although it is recognized that enough metal must be present
to achieve reasonable carbonylation reaction rates; excess metal on
the other hand may on occasion result in undesired by-product
formation. In certain embodiments, the rhodium concentration is
from about 200 to about 1200 ppm (about 2.times.10.sup.-3 to about
13.times.10.sup.-3 M). In other embodiments, the rhodium
concentration is from about 400 to about 1000 ppm (about
4.times.10.sup.-3 to about 10.times.10.sup.-3 M). The amount of
rhodium used is not a critical feature and higher concentrations
are acceptable, subject to economic considerations.
[0046] Suitable iridium catalysts are taught, for example, by U.S.
Pat. No. 5,932,764. Suitable iridium catalysts include iridium
metal and iridium compounds. Examples of suitable iridium compounds
include IrCl.sub.3, IrI.sub.3, IrBr.sub.3, [Ir(CO).sub.2I].sub.2,
[Ir(CO).sub.2Cl].sub.2, [Ir(CO).sub.2Br].sub.2,
[Ir(CO).sub.4I.sub.2].sup.-H.sup.+, [Ir(CO).sub.2].sup.-H.sup.+,
[Ir(CO).sup.2I.sub.2].sup.-H.sup.+,
[Ir(CH.sub.3)I.sub.3(CO).sub.2].sup.-H.sup.+, Ir.sub.4(CO).sub.12,
IrCl.sub.3.4H.sub.2O, IrBr.sub.3.4H.sub.2O, Ir.sub.3(CO).sub.12,
Ir.sub.2O.sub.3, IrO.sub.2, Ir(acac)(CO).sub.2, Ir(acac).sub.3,
Ir(Ac).sub.3, [Ir.sub.3O(OAc).sub.6(H.sub.2O).sub.3][OAc], and
H.sub.2[IrCl.sub.6]. In certain embodiment, the iridium compounds
are selected from the group consisting of acetates, oxalates,
acetoacetates, the like, and mixtures thereof. In certain
embodiments, the iridium compounds are acetates.
[0047] In certain embodiments, the iridium catalyst is used with a
co-catalyst. Preferred co-catalysts include metals and metal
compounds selected from the group consisting of osmium, rhenium,
ruthenium, cadmium, mercury, zinc, gallium, indium, and tungsten,
their compounds, the like, and mixtures thereof. In other
embodiments, the co-catalysts are selected from the group
consisting of ruthenium compounds and osmium compounds. In other
embodiments, the co-catalysts are ruthenium compounds. In other
embodiments, the co-catalysts are chloride-free such as
acetates.
[0048] As indicated above, the carbonylation system 1 includes
catalytic component, e.g., a rhodium-containing component, as
described above, and a liquid reaction medium which generally
comprises methyl acetate, methyl iodide and acetic acid and at
least one additive, which improves catalytic component stability
and reduces added water concentration. In certain embodiments, the
added water can be reduced substantially to zero.
[0049] In the practice of the invention, water is deliberately
introduced in selected amounts into the carbonylation system. The
concentration of water present in carbonylation system to which the
instant invention relates is from about 0.5 wt. % to about 12 wt. %
(about 0.03 to about 7.5 M) based on total weight of the
carbonylation system inclusive of all additives. In certain
embodiments, the concentration of water present in the
carbonylation system is from about 1 to about 3 wt. % (about 0.65
to about 7M); most preferably about 4 to about 9 wt. % water is
present.
[0050] In accordance with the present invention, the ratio of water
to rhodium employed in the present is from about 4000:1 to about
200:1. In certain embodiment, the ratio of water to rhodium
employed in the present invention is from about 1750:1 to about
270:1.
[0051] Another component of the liquid reaction medium aspect of
the carbonylation system to which the instant invention pertains is
methyl acetate, which can be charged into the reactor or can be
formed in-situ in an amount of from about 0.5 to about 10 wt. %
based on the total weight of the liquid reaction medium. The
foregoing wt. % range of methyl acetate corresponds to a methyl
acetate molarity of from about 0.07 to about 1.4 M. More
preferably, the concentration of methyl acetate employed in the
process of the present invention is from about 1 to about 8 wt. %
(about 0.14 to about 1.1 M).
[0052] The corresponding ratio of methyl acetate to rhodium
employed in the present invention is from about 700:1 to about 5:1.
In other embodiments, the ratio of methyl acetate to rhodium is
from about 275:1 to 14:1.
[0053] A third component of the subject liquid reaction medium is
methyl iodide (MeI), which can be added directly to or can be
formed in-situ by using HI. In certain embodiments, the
concentration of MeI employed in the instant invention is from
about 0.6 to about 36 wt. % (0.05 to about 3 M). In certain
embodiments, the concentration of MeI employed in the instant
invention is from about 3.6 to about 24 wt. % (about 0.3 to about
2.0M). When HI is employed, it is generally present in a
concentration of from about 0.6 to about 23 wt. % (0.05 to about
2.0 M). In certain embodiments, the concentration of HI is from
about 2.3 to about 11.6 wt. % (0.2 to about 1.0 M).
[0054] The fourth component of the liquid reaction medium is acetic
acid (HOAc), which is typically present in the reactor in an amount
of from about 20 to about 80 wt. %. The corresponding molarity
range being from about 3 to about 12 M. In certain embodiments, the
amount of acetic acid that is charged into the reactor is from
about 35 to about 65 wt. % (about 5 to about 10 M).
[0055] Hydrogen may also be fed into the reactor to increase the
overall rate of the carbonylation process. In this embodiment,
improved carbonylation efficiency can be obtained when the addition
of hydrogen to the reactor maintains a concentration of from about
0.1 to about 5 mole % H.sub.2, based on the total number of moles
of CO in the reactor. In certain embodiments, hydrogen addition is
sufficient to maintain a concentration of from about 0.5 to about 3
mole % H.sub.2 in the reactor. Hydrogen may be added to the reactor
either as a separate stream or together with carbon monoxide;
make-up amounts can be introduced in the same manner, as needed, to
maintain the hydrogen concentration at the levels defined
hereinabove.
[0056] The carbonylation process of the present invention, which
does not evince any induction time for carbonylation, can be
carried out either in a batch or continuous mode. When operating in
a continuous mode, the reaction system hardware usually comprises
(a) a liquid phase carbonylation reactor, (b) a so-called
"flasher", and (c) a methyl iodide-acetic acid splitter column.
Other reaction zones or distillation columns may be present. Such
hardware and the operation thereof are well known in the art. When
operating in a continuous mode, the carbonylation reactor is
typically a stirred autoclave within, which the concentration of
the reactants are maintained automatically at a constant level. The
present invention also contemplates with low volatility additives
and minimum water, a continuous reactor system that does not
include a separate flasher, but where a crude product stream is
removed as a gas, where the distillation subsystem removes MeI and
water for recycling to the reaction.
[0057] The carbonylation processes to which the instant invention
relates is, for either mode, typically conducted under a pressure
of from about 200 to about 1200 psig. In certain embodiments, the
carbonylation is conducted under a pressure of about 300 to about
600 psig.
[0058] The carbonylation processes to which the present invention
relates is typically carried out at a temperature of from about
160.degree. C. to about 220.degree. C. In certain embodiments,
carbonylation is carried out at a temperature of from about
170.degree. C. to about 200.degree. C.
[0059] In practice, carbonylation reaction time varies, depending
upon reaction parameters, reactor size and charge, and the
individual components employed.
Experiments of the Invention
Acetic Acid Experimental Procedures
[0060] These details are intended for a 300 cc stirred autoclave of
Hasteloy, Zirconium or similar corrosion resistant material.
Amounts should be adjusted if a different reactor volume is used.
The reactor head should be equipped with attachments for cooling
coils, thermocouples and dip tubes for sampling and additions under
pressure. A means for feeding CO to the reactor from a high
pressure reservoir via a regulator should be provided. The
reservoir should have a pressure transducer to monitor pressure
drop versus time as a means to measure carbonylation rate.
Alternately, the CO reservoir could be placed on a scale and CO
consumption monitored by weight change. The set up used is a 250 cc
reservoir pressurized to between about 1200 and about 1600 psi. A
larger reservoir at about 1000 psi could also be used if a
compressor is not available.
[0061] Reaction components, minus the catalyst, should be charged
to the reactor according to the experimental table and the reactor
assembled per manufacturer directions. The reactor is then leak
tested with nitrogen and purged with carbon monoxide. At this point
the reactor is pressurized with CO to 100 psig and heated to
186.degree. C. with agitation. The reaction is initiated by
injection of a rhodium-containing solution to the reactor contents,
adjusting reactor pressure to 400 psig and adjusting the
temperature to 186.degree. C. These conditions are maintained for
one hour.
[0062] At appropriate time intervals as specified (15-20 minutes),
samples are removed from the reactor for FTIR and GC analysis. FTIR
analysis of the liquid will measure Rh (I) peaks at 1990 and 2060
cm.sup.-1 and a Rh (III) peak at 2090 cm.sup.-1 using a liquid
cell. Analysis of the liquid will quantify acetic acid, methyl
acetate and methyl iodide. At the end of the reaction, the reactor
headspace gas should be sampled and analyzed for carbon dioxide and
hydrogen to measure the water gas shift reaction.
[0063] The active rhodium compound is [H][Rh(CO).sub.2I.sub.2].
This compound is generated in situ immediately after injection of a
rhodium acetate pre-catalyst solution. Rhodium acetate is readily
soluble in acetic acid containing 10% water. The solution is stable
in air at room temperature such that sufficient solution can be
prepared for a full week of experimentation. The rhodium
concentration should be high enough to provide 500 ppm rhodium in
the reactor from the injected solution. For 150 cc of 500 ppm Rh
reactor solution with 20 cc rhodium solution injected this would
require 3750 ppm rhodium in the stock solution. For 5 runs the
basic recipe for the rhodium stock solution is to dissolve 1.164
grams rhodium acetate into 110 mL acetic or propionic acid
containing 10% water. Rhodium acetate solid (CAS# 42204-14-8) is
available from Alfa Aesar (catalog number-43004).
Preparation of Rhodium Stock Solution
[0064] A 25 cc round bottom flask fitted with magnetic stirrer and
septum closure was purged with carbon monoxide. To this flask was
added 0.0235 grams dichloro tetracarbonyl rhodium (I) (CAS #
14523-22-9), 20 mL of glacial acetic acid, 0.4 gram of water and 1
drop of hydriodic acid (55-57%). The solution was stirred at room
temperature and sparged for 10 minutes with carbon monoxide via a
two needle arrangement through the septum. An FTIR spectrum was
taken after 10 minutes to confirm the formation of diiodo
dicarbonyl rhodium (I) by observation of peaks at 1990 and 2060
cm.sup.-1.
Rhodium (I) Stability Experiments
[0065] To a series of glass vials was added stabilizing compounds
in the amounts listed in the table below. To each vial in turn was
added 2 drops of an 8:1 solution of acetic acid and hydriodic acid.
To each vial was then added 0.5 mL of rhodium stock solution
prepared as indicated above. The solution was sparged at room
temperature for 6 minutes and a sample was removed for immediate
FTIR analysis to measure Rh(I)/Rh(III) ratio.
TABLE-US-00002 TABLE 2 Additive Amount and Rh(I) to Rh(III) Ratio
Amount Rh(I)/ Experiment Additive (g) Rh(III) A potassium sulfite
(Na.sub.2SO.sub.3) 0.082 4.8 B poly vinyl alcohol (pVA) 0.144 4.5 C
tetrabutyl ammonium iodide (t-Bu.sub.4NI) 0.111 1.3 D trimethyl
phosphate (Me.sub.3PO) 0.037 1.3 E diethylene glycol dibutyl ether
0.107 1 F potassium sulfate (KSO.sub.4) 0.098 1 G poly methacrylic
acid (pMAA) 0.023 0.9 H potassium iodide (KI) 0.117 0.4 I 14% water
0.59 0 J 2% water NA 0 K trifluoroacetic acid (TFA) 0.277 0 L
p-toluene sulfonic acid (TSA) 0.138 0
[0066] To a series of experiments conducted in a 300 cc stirred
reactor outfitted as described above were added the
hydrogen-bonding additives as shown in Table 3.
TABLE-US-00003 TABLE 3 Reactor Inputs Amount MeI AcOMe or Amount
Added Water Rh SS.sup..dagger-dbl. Run Solvent (mL) (g) Propionate
Additive (g) (g) (mL) 1 Propionic 98.4 10.6 9.25 14% water control
0 17.6 20 2 Propionic 115 10.6 9.25 2% water control 0 1 20 3
Propionic 115 10.6 9.25 .phi.SO.sub.2.phi..sup..dagger-dbl. 12 1 20
4 Propionic 115 10.6 9.25 pMAA 6 1 20 5 Propionic 115 10.6 9.25
PVOH 12 1 20 6 Propionic 115 10.6 9.25 Boric Acid 6 1 20 7
Propionic 115 10.6 9.25 Citric Acid 6 1 20 8 Propionic 115 10.6
9.25 Succinic Acid 6 1 20 .sup..dagger.Rhodium stock solution of
dichloro tetracarbonyl rhodium (I) .sup..dagger-dbl.diphenyl
sulfone
[0067] The reaction was then conducted at 400 psig with carbon
monoxide make-up to maintain pressure and at a temperature of
186.degree. C. FTIR (Fourier Transform Infra Red spectrometry) was
used to determine Rh(I) and Rh(III) concentrations, while gas
chromatography was used to analyze and characterize all gas and
liquid components of the reaction media. Analysis of this series of
experiments are tabulated in Table 4.
TABLE-US-00004 TABLE 4 Results of Analysis of This Series of
Experiments Moles Moles Moles Grams Moles AcOH AcOMe MeI CO CO %
H.sub.2 Additive % Rh(I) % Rh(I) Produced Consumed Consumed
Consumed Consumed (WGS) 0 mins 20 mins 14% Water 80 33 0.145 0.1055
0.05 3.2 0.114 56.0 2% Water No Additive 45 20 0.060 0.062 0.008
1.5 0.054 16.6 Phenyl Sulfone 50 60 0.090 0.090 0.005 1.2 0.043
1.80 Sodium Fluoride 86 84 0.060 0.004 0.060 1.5 0.054 0.50
pMAA.sup..dagger..dagger. 100 64 0.059 0.057 0.004 1.9 0.068 15.3
pVOH.sup..dagger-dbl. 70 42 0.082 0.063 0.017 2.5 0.089 0.90 Boric
Acid 61 41 0.041 0.035 0.001 1.6 0.057 18.3 Citric Acid 86 37 0.086
0.086 0.008 2.1 0.075 3.90 Succinic Acid 83 35 0.067 0.070 0.008
1.8 0.064 13.5 .sup..dagger..dagger.pMAA is polymetharcylic acid
.sup..dagger-dbl.pVOH is polyvinylalcohol
[0068] The above data shows that phenyl sulfone, pMAA, pVOH, boric
acid, citric acid, and succinic acid are effective additives for
the production of acetic acid from methanol as the amount of acetic
acid (AcOH) produced is nearly identical to the amount of methyl
acetate (AcOMe) consumed, while maintaining the amount of methyl
iodide (MeI) substantially constant, only 0.004 moles of MeI was
consumed during the reaction, where substantially constant means
that the amount of MeI consumed is less than about 0.02 moles.
[0069] The following table tabulates the Rh(I) active factor for
the examples of Table 4.
TABLE-US-00005 TABLE 5 Amounts of Rh Active Factor Present in the
Reactions Moles Additive Rh*AA.sup..dagger. % Rh
(I).sup..dagger-dbl. Acetic Acid Produced 14% Water 4.785 33 0.145
2% Water 1.2 20 0.06 Phenyl Sulfone 5.4 60 0.09 pMAA 3.776 64 0.059
pVOH 3.444 42 0.082 Boric Acid 1.681 41 0.041 Citric Acid 3.182 37
0.086 Succinic Acid 2.345 35 0.067 .sup..dagger.Rhodium Active
Factor .sup..dagger-dbl.20 minutes
[0070] The data show that all of additives showed improved results
relative to 2 wt. % added water, and all increased % Rh(I) by at
least a factor of 2 relative to the examples with 2 wt. % added
water. Surprisingly, all but boric acid showed results approaching
the value of the 14 wt. % added water example, but having only 2
wt. % added water. The data clearly indicate the surprising and
unexpected results that these additive, alone or in combination,
are effective for their intended purpose in the carbonylation of
alkyl alcohols into carboxylic acids having on additional carbon
atom, such as the carbonylation of methanol to acetic acid.
[0071] All references cited herein are incorporated by reference.
Although the invention has been disclosed with reference to its
preferred embodiments, from reading this description those of skill
in the art may appreciate changes and modification that may be made
which do not depart from the scope and spirit of the invention as
described above and claimed hereafter.
* * * * *