Organic compounds -- part of the class 532-570 series – Organic compounds – Persulphonic acids or salts thereof
Reexamination Certificate
2000-05-22
2002-08-27
Richter, Johann (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Persulphonic acids or salts thereof
C562S519000, C562S537000
Reexamination Certificate
active
06441222
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for the vapor phase carbonylation of alkyl alcohols, ethers and ester-alcohol mixtures to produce esters and carboxylic acids, and particularly the carbonylation of methanol to produce acetic acid and methyl acetate. More particularly, the present invention relates to a vapor phase carbonylation using a supported catalyst which includes a catalytically effective amount of iridium and gold.
BACKGROUND OF THE INVENTION
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, as illustrated in equations 1-3 below:
ROH+CO→RCOOH (1)
2ROH+CO→RCOOR+water (2)
ROR+CO→RCOOR (3)
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. However, solid heterogeneous carbonylation catalysts offer the potential advantages of easier product separation, lower cost materials of construction, facile recycle, and even higher rates. The use of solid carbonylation catalyst in a vapor phase carbonylation reaction is especially beneficial due to the fact that operating in the vapor phase eliminates catalyst dissolution, i.e., metal leaching from the catalyst support, which occurs in the known heterogeneous processes operating in the presence of liquid compounds.
Rhodium was the first heterogeneous catalyst used in vapor phase carbonylation. 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 goes further to describe 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. Schultz teaches that these elements are useful to promote the rhodium activity, but do not themselves provide carbonylation catalysis. Uhm, in U.S. Pat. No. 5,488,143, describes the use of the alkali metals Li, Na, K, Rb, and Cs, the alkaline earth metals Be, Mg, Ca, Sr, and Ba, or the transition metals Co, Ru, Pd, Pt, Os, Ir, N-i, Mn, Re, Cr, Mo, W, V, Nb, Ta, Ti, Zr, and Hr as promoters for supported rhodium for the halide-promoted, vapor phase methanol carbonylation reaction. Further, 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.
Iridium is also 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.
U.S. Pat. No. 5,510,524 teaches that the addition of rhenium improves the rate and stability of both the Ir-I and Rh-I homogeneous catalyst systems.
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.
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.
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.
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 attached to an oxide support.
Nickel on activated carbon has been studied as a heterogeneous catalyst for the halide-promoted vapor phase carbonylation of methanol, and increased rates are observed when hydrogen is added to the feed mixture. Relevant references to the nickel-on-carbon catalyst systems are provided by Fujimoto et al. in
Chemistry Letters
(1987) 895-898 and in
Journal of Catalysis
, 133 (1992) 370-382 and in the references contained therein. Liu et al., in
Ind. Eng. Chem. Res
., 33 (1994) 488-492, report that tin enhances the activity of the nickel-on-carbon catalyst. Mueller et al., in U.S. Pat. No. 4,918,218, disclose the addition of palladium and optionally copper to supported nickel catalysts for the halide-promoted carbonylation of methanol. In general, the rates of reaction provided by nickel-based catalysts are lower than those provided by the analogous rhodium-based catalysts when operated under similar conditions.
Other single metals supported on carbon have been reported by Fujimoto et al. in
Catalysis Letters
, 2 (1989) 145-148 to have limited activity in the halide-promoted vapor phase carbonylation of methanol. The most active of these metals is Sn. Following Sn in order of decreasing activity are Pb, Mn, Mo, Cu, Cd, Cr, Re, V, Se, W, Ge and Ga. None of these other single metal catalysts are nearly as active as those based on Rh, Ir, or Ni.
U.S. Pat. No. 5,218,140, to Wegman, describes a vapor phase process for converting alcohols and ethers to carboxylic acids and esters by the
Carver Donald Lee
Singleton Andy Hugh
Tustin Gerald Charles
Zoeller Joseph Robert
Eastman Chemical Company
Forohar Farhad
Johnston Susan E.
Richter Johann
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