Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2000-03-24
2001-05-01
Geist, Gary (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
Reexamination Certificate
active
06225498
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to the removal of iodides from organic media and more particularly to the removal of higher iodides, such as dodecyl iodide from acetic acid and/or acetic anhydride manufactured by utilizing a rhodium-lodide catalyst system.
BACKGROUND ART
Perhaps the most widely used process for the manufacture of acetic acid, the well known Monsanto process, involves carbonylating methanol in the presence of rhodium, methyl iodide, methyl acetate and water. The product is suitable for all purposes; however, iodide contamination is an issue with respect to acetic acid made by way of the Monsanto process or in acetic anhydride manufactured by way of a rhodium-iodide catalyst system.
It was discovered by Hilton that macroreticulated, strong acid cationic exchange resins with at least one percent of their active sites converted to the silver or mercury form exhibited remarkable removal efficiency for iodide contaminants in acetic acid or other organic media. The amount of silver or mercury associated with the resin may be from as low as about one percent to as high as 100 percent. Preferably about 25 percent to about 75 percent of the active sites were converted to the silver or mercury form and most preferably about 50 percent. There is disclosed in U.S. Pat. no. 4,615,806 removal of various iodides from acetic acid. In particular there is shown in the examples removal of methyl iodide, HI, I
2
and hexyl iodide.
Various embodiments of the basic invention disclosed in U. S. Pat. No. 4,615,806 have subsequently appeared in the literature. There is shown in U.S. Pat. No. 5,139,981 to Kurland a method for removing iodides from liquid carboxylic acid contaminated with a halide impurity by contacting the liquid halide contaminant acid with a silver (I) exchanged macroreticular resin. The halide reacts with the resin bound silver and is removed from the carboxylic acid stream. The invention in the '981 patent more particularly relates to an improved method for producing the silver exchanged macroreticular resins suitable for use in iodide removal from acetic acid.
U.S. Pat. no. 5,227,524 to Jones discloses a process for removing iodides using a particular silver-exchanged macroreticular strong acid ion exchange resin. The resin has from about 4 to about 12 percent cross-linking, a surface area in the proton exchanged form of less than 10 m2/g after drying from the water wet state and a surface area of greater than 10 m
2
/g after drying from a wet state in which the water has been replaced by methanol. The resin has at least one percent of its active sites converted to the silver form and preferably from about 30 to about 70 percent of its active sites converted to the silver form.
U.S. Pat. No. 5,801,279 to Miura et al discloses a method of operating a silver exchanged macroreticular strong acid ion exchange resin bed for removing iodides from a Monsanto type acetic acid stream. The operating method involves operating the bed while elevating the temperatures in stages and contacting the acetic acid and/or acetic anhydride containing the iodide compounds with the resins. Exemplified in the patent is the removal of hexyl iodide from acetic acid at temperatures of from about 25° C. to about 45° C.
So also, other ion exchange resins have been used to remove iodide impurities from acetic acid and/or acetic anhydride. There is disclosed in U.S. Pat. No. 5,220,058 to Fish et al the use of ion exchange resins having metal exchanged thiol functional groups for removing iodide impurities from acetic acid and/or acetic anhydride. Typically, the thiol functionality of the ion exchange resin has been exchanged with silver, palladium, or mercury.
There is further disclosed in European Publication No. 0 685 445 A1 a process for removing iodide compounds from acetic acid. The process involves contacting an iodide containing acetic acid stream with a polyvinylpyridine at elevated temperatures to remove the iodides. Typically, the acetic acid was fed to the resin bed according to the '445 publication at a temperature of about 100° C.
With ever increasing cost pressures and higher energy prices, there has been ever increasing motivation to simplify chemical manufacturing operations and particularly to reduce the number of manufacturing steps. In this regard, it is noted that in U.S. Pat. No. 5,416,237 to Aubigne et aL there is disclosed a single zone distillation process for making acetic acid. Such process modifications, while desirable in terms of energy costs, tend to place increasing demands on the purification train. In particular, fewer recycles and fewer purification steps tend to introduce (or fail to remove) a higher level of iodides into the product stream and particularly more iodides of a higher molecular weight. For example, octyl iodide, decyl iodide and dodeycl iodides may all be present in the product stream as well as hexadecyl iodide.
The prior art resin beds operated as described above do not efficiently and quantitatively remove higher organic iodides from organic media such as acetic acid or acetic acid streams as required by certain end uses, particularly the manufacture of vinyl acetate monomer. Accordingly, an object of the present invention is to provide for the efficient and nearly quantitative removal of higher organic iodides from an acetic acid and/or acetic anhydride product stream.
SUMMARY OF INVENTION
There is provided in a first aspect of the present invention, a method of removing organic iodides from non-aqueous organic media comprising contacting the organic media with a silver or mercury exchanged cationic ion exchange substrate at a temperature greater than about 50° C. Generally the organic media contains organic iodides with an aliphatic chain length of C10 or greater. In many embodiments the organic media contains organic iodides at least about 25 percent by weight of which have an aliphatic chain length of C10 or greater. In still other embodiments at least about 50 percent of the organic iodides include organic iodides having a chain length of C10 or greater. Such iodides may be selected from the group consisting of decyl iodide and dodecyl iodide. Preferably the treatment of the organic media is effective to remove at least about 90 percent by weight of the decyl iodides and dodecyl iodides from the organic media. Organic media in some embodiments contains total iodides in the range of from about 10 ppb to about 1000 ppb. More typically the organic media contains from about 250 ppb total iodide to about 750 ppb total iodide. Treatment of the organic media in accordance with the present invention preferably removes at least about 99 percent of the total iodides from the organic media
There is provided in accordance with another aspect of the present invention a method of removing iodides from acetic acid or acetic anhydride including the steps of: (1) providing a stream of acetic acid or acetic anhydride with an organic iodide content wherein at least about 20 percent of said organic iodides comprise C10 or higher molecular weight organic iodides; (2) contacting said stream with a macroreticular, strong acid, ion exchange resin wherein at least about one percent of the active sites of the resin have been converted to the silver or mercury form. The bed is operated at a temperature (that is, the resin is maintained at a temperature) of at least about 50° C. and is operative to remove at least about 90 percent of the organic iodides in the stream of acetic acid or acetic anhydride. Most typically, the method is practiced on an acetic acid stream. Typical temperatures may include temperatures of at least about 60° C., at least about 70° C. or at least about 80° C. depending upon the flow rates and the nature of the iodides sought to be removed. The upper limit may be about 100° C. or up to 150° C. provided the resin selected is stable at these temperatures.
Most typically the resin is a sulfonic acid functionalized resin, wherein from about 25 to about 75 percent of the active sites have been converted to the sil
Blay George A.
Broussard Jerry A.
Torrence G. Paull
Calve John N.
Celanese International Corporation
Ferrell Michael W.
Geist Gary
Mullen James J.
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