Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2001-06-20
2003-11-11
Rotman, Alan L. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C562S550000, C562S517000, C562S519000, C562S607000, C560S232000
Reexamination Certificate
active
06646154
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a vapor-phase carbonylation method for producing esters and carboxylic acids from reactants including lower alkyl alcohols, lower alkyl alcohol producing compositions, and mixtures thereof. More particularly, the present invention relates to a method for the vapor-phase carbonylation of methanol and/or a methanol producing source to produce acetic acid, methyl acetate and mixtures thereof using a catalyst having a catalytically effective amount of a Group VIII metal selected from platinum or palladium, and tungsten, wherein the metals are associated with a solid carrier material.
Lower carboxylic acids and esters such as acetic acid and methyl acetate have been known as industrial chemicals for many years. Acetic acid is used in the manufacture of a variety of intermediary and end-products. For example, an important derivative is vinyl acetate which can be used as monomer or co-monomer for a variety of polymers. Acetic acid itself is used as a solvent in the production of terephthalic acid, which is widely used in the container industry, and particularly in the formation of PET beverage containers.
There has been considerable research activity in the use of metal catalysts for the carbonylation of lower alkyl alcohols, such as methanol, and ethers to their corresponding carboxylic acids and esters.
Carbonylation of methanol is a well known reaction and is typically carried out in the liquid phase with a catalyst. A thorough review of these commercial processes and other approaches to accomplishing the formation of acetyl from a single carbon source is described by Howard et al. in
Catalysis Today,
18 (1993) 325-354. Generally, the liquid phase carbonylation reaction for the preparation of acetic acid using methanol is performed using homogeneous catalyst systems comprising a Group VIII metal and iodine or an iodine-containing compound such as hydrogen iodide and/or methyl iodide. Rhodium is the most common Group VIII metal catalyst and methyl iodide is the most common promoter. These reactions are conducted in the presence of water to prevent precipitation of the catalyst. For example, U.S. Pat. No. 5,510,524 to Garland et. al. describes a liquid phase carbonylation process for the production of carboxylic acid by carbonylation of an alkyl alcohol and/or reactive derivative by contacting the alcohol with carbon monoxide in a liquid reaction composition which includes an iridium catalyst or rhodium catalyst, an alkyl halide, water and a rhenium promoter.
A disadvantage of a homogeneous phase carbonylation process is that additional steps are necessary for separating the products from the catalyst solutions, and there are always handling losses of the catalyst. Losses of the metal in the catalyst can be attributed to several factors, such as the plating-out of the active metal onto piping and process equipment thereby rendering the metal inactive for carbonylation purposes and losses due to incomplete separation of the catalyst from the products. These losses of the metal component are costly because the metals themselves are very expensive.
U.S. Pat. No. 5,144,068 describes the inclusion of lithium in the catalyst system which allows the use of less water in the Rh-I homogeneous process. Iridium also is an active catalyst for methanol carbonylation reactions but normally provides reaction rates lower than those offered by rhodium catalysts when used under otherwise similar conditions.
European Patent Application EP 0 752 406 A1 teaches that ruthenium, osmium, rhenium, zinc, cadmium, mercury, gallium, indium, or tungsten improve the rate and stability of the liquid phase Ir—I catalyst system. Generally, the homogeneous carbonylation processes presently being used to prepare acetic acid provide relatively high production rates and selectivity. However, heterogeneous catalysts offer the potential advantages of easier product separation, lower cost materials of construction, facile recycle, and even higher rates.
Schultz, in U.S. Pat. No. 3,689,533, discloses using a supported rhodium heterogeneous catalyst for the carbonylation of alcohols to form carboxylic acids in a vapor phase reaction. Schultz further discloses the presence of a halide promoter.
Schultz in U.S. Pat. No. 3,717,670 describes a similar supported rhodium catalyst in combination with promoters selected from Groups IB, IIIB, IVB, VB, VIB, VIII, lanthanide and actinide elements of the Periodic Table.
Uhm, in U.S. Pat. No. 5,488,143, describes the use of alkali, alkaline earth or transition metals as promoters for supported rhodium for the halide-promoted, vapor phase methanol carbonylation reaction. Pimblett, in U.S. Pat. No. 5,258,549, teaches that the combination of rhodium and nickel on a carbon support is more active than either metal by itself.
In addition to the use of iridium as a homogeneous alcohol carbonylation catalyst, Paulik et al., in U.S. Pat. No. 3,772,380, describe the use of iridium on an inert support as a catalyst in the vapor phase, halogen-promoted, heterogeneous alcohol carbonylation process.
European Patent Applications EP 0 120 631 A1 and EP 0 461 802 A2 describe the use of special carbons as supports for single transition metal component carbonylation catalysts.
European Patent Application EP 0 759 419 A1 pertains to a process for the carbonylation of an alcohol and/or a reactive derivative thereof.
EP 0 759 419 A1 discloses a carbonylation process comprising a first carbonylation reactor wherein an alcohol is carbonylated in the liquid phase in the presence of a homogeneous catalyst system and the off gas from this first reactor is then mixed with additional alcohol and fed to a second reactor containing a supported catalyst. The homogeneous catalyst system utilized in the first reactor comprises a halogen component and a Group VIII metal selected from rhodium and iridium. When the Group VIII metal is iridium, the homogeneous catalyst system also may contain an optional co-promoter selected from the group consisting of ruthenium, osmium, rhenium, cadmium, mercury, zinc, indium and gallium. The supported catalyst employed in the second reactor comprises a Group VIII metal selected from the group consisting of iridium, rhodium, and nickel, and an optional metal promoter on a carbon support. The optional metal promoter may be iron, nickel, lithium and cobalt. The conditions within the second carbonylation reactor zone are such that mixed vapor and liquid phases are present in the second reactor. The presence of a liquid phase component in the second reactor inevitably leads to leaching of the active metals from the supported catalyst which, in turn, results in a substantial decrease in the activity of the catalyst.
The literature contains several reports of the use of rhodium-containing zeolites as vapor phase alcohol carbonylation catalysts at one bar pressure in the presence of halide promoters. The lead references on this type of catalyst are presented by Maneck et al. in
Catalysis Today,
3 (1988), 421-429. Gelin et al., in
Pure
&
Appl. Chem.,
Vol 60, No. 8, (1988) 1315-1320, provide examples of the use of rhodium or iridium contained in zeolite as catalysts for the vapor phase carbonylation of methanol in the presence of halide promoter. Krzywicki et al., in
Journal of Molecular Catalysis,
6 (1979) 431-440, describe the use of silica, alumina, silica-alumina and titanium dioxide as supports for rhodium in the halide-promoted vapor phase carbonylation of methanol, but these supports are generally not as efficient as carbon. Luft et al., in U.S. Pat. No. 4,776,987 and in related disclosures, describe the use of chelating ligands chemically attached to various supports as a means to attach Group VIII metals to a heterogeneous catalyst for the halide-promoted vapor phase carbonylation of ethers or esters to carboxylic anhydrides.
Evans et al., in U.S. Pat. No. 5,185,462, describe heterogeneous catalysts for halide-promoted vapor phase methanol carbonylation based on noble metals attached to nitrogen or phosphorus ligands
Carver Donald Lee
Singleton Andy Hugh
Tustin Gerald Charles
Zoeller Joseph Robert
Eastman Chemical Company
Graves, Jr. Bernard J.
Oh Taylor V.
Rotman Alan L.
Wood Jonathan
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