Catalyst – solid sorbent – or support therefor: product or process – Regenerating or rehabilitating catalyst or sorbent – Treating with a liquid or treating in a liquid phase,...
Reexamination Certificate
1998-12-18
2001-02-20
Griffin, Steven P. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Regenerating or rehabilitating catalyst or sorbent
Treating with a liquid or treating in a liquid phase,...
C502S022000, C502S027000, C210S681000, C210S688000
Reexamination Certificate
active
06191060
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to methods for reclaiming metal catalyst species. In particular, this invention relates to methods for isolating and recycling palladium and cobalt catalysts used in the production of diaryl carbonates.
Diaryl carbonates, and diphenyl carbonate in particular, are valuable monomer precursors for the preparation of polycarbonates by melt transesterification. An advantageous route for the synthesis of diaryl carbonates is the direct carbonylation of aromatic hydroxy compounds by carbon monoxide and an oxidant in the presence of a catalyst.
A wide range of catalysts may be used in this preparation of diaryl carbonates. For example, U.S. Pat. No. 4,187,242 to Chalk discloses catalysts derived from Group VIIIB metals, i.e., metals selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium and platinum, or complexes thereof. U.S. Pat. Nos. 5,231,210 to Joyce, et al., U.S. Pat. Nos. 5,284,964 and 5,760,272 to Pressman et al., and 5,399,734 to King, Jr., et al. further disclose the use of co-catalysts, including metal co-catalyst species such as cobalt pentadentate complexes and complexes of cobalt with pyridines, bipyridines, terpyridines, quinolines, isoquinolines, aliphatic polyamines such as ethylenediamine, crown ethers, aromatic or aliphatic amine ethers such as cryptanes, and Schiff bases, in combination with organic co-catalysts such as terpyridines and quaternary ammonium or phosphonium halides. In U.S. Pat. No. 5,498,789 to Takagi et al., the catalyst system consists of a palladium compound, at least one lead compound, at least one halide selected from quaternary ammonium halides and quaternary phosphonium halides, and optionally at least one copper compound.
As can be seen from the above brief review, the crude reaction mixtures arising from the production of diaryl carbonates can contain complex mixtures of catalyst and co-catalyst metals, and organic products and by-products. The cost of commercially implementing direct oxidative carbonylation is heavily dependent on a combination of the efficiency of the catalyst package and on the ability to reclaim the expensive catalyst components and unconverted aromatic starting material. While palladium represents the primary material expense, it is also important to control the usage of other, less expensive materials, such as cobalt, manganese, or lead both from the cost and environmental points of view. Accordingly, there remains a need in the art for efficient, convenient methods for the reclamation of the metal catalysts and cocatalysts used in the carbonylation of aromatic hydroxy compounds to produce diary carbonates.
SUMMARY OF THE INVENTION
The above-discussed and other drawbacks and deficiencies of the related art are alleviated by the method of the present invention for reclaiming metal catalyst species from aqueous extract streams arising from the crude reaction mixtures produced by oxidative carbonylation of aromatic hydroxy compounds, comprising treating metal-containing aqueous extract streams with a precipitating agent effective to selectively precipitate at least one metal separately or as a mixture from the treated extract. Such reclamation substantially reduces both economic and environmental concerns in the preparation of diaryl carbonates.
DETAILED DESCRIPTION OF THE INVENTION
The present method makes possible efficient reclamation of metal catalyst and/or co-catalyst species (referred to hereinafter collectively as “metal catalysts”), particularly palladium and cobalt, from crude mixtures resulting from the production of diaryl carbonates. The method comprises treating metal-containing aqueous extract streams containing ruthenium, rhodium, palladium, osmium, iridium, platinum, iridium, manganese, lead, zinc, cobalt, copper, and mixtures thereof with a precipitating agent effective to selectively precipitate the metals separately or as a mixture from the treated extract. In a preferred embodiment, palladium and cobalt are precipitated together or separately.
The crude reaction mixture obtained when diaryl carbonates are made by direct oxidative carbonylation of aromatic hydroxy compounds contains the excess starting aromatic hydroxy compounds, the product diaryl carbonate, and organic and inorganic by-products. The catalyst metals in this crude reaction mixture, e.g., ruthenium, rhodium, palladium, osmium, iridium, platinum, iridium, manganese, lead, zinc, copper, cobalt, and mixtures thereof, may be removed by solvent extraction using an aqueous acid, aqueous salt, or aqueous acid/salt mixture.
Generally, species effective to extract the catalyst metals include strong electrolytes with high water solubility (to enable phase separation with the organic phase), low hydroxyaryl and diaryl carbonate solubility, and strong complexing affinities with the metals to be extracted, particularly palladium. Acids are most useful for palladium extraction.
Preferred acids include, but are not limited to, inorganic acids such as hydrochloric acid and hydrobromic acid. Salts effective in metal extraction include, but are not limited to, alkali metal and alkaline earth salts of halides. Preferred salts are sodium, potassium, calcium, and magnesium salts of chlorine and bromine, particularly sodium chloride and sodium bromide. Combinations of the foregoing acids and salts may also be used.
The concentration of acid or acid/salt mixture effective to extract the metal catalysts from the crude reaction mixture is readily empirically determined by one of ordinary skill in the art. In general, an effective concentration is in the range from about 1 percent by weight to about 18 percent by weight, and preferably in the range from about 3 percent by weight to about 10 percent by weight.
Reclamation of metals from the extract is achieved by the addition of a precipitating agent which forms an effectively water-insoluble compound with the catalyst metals. Effective precipitating agents have at least partial water solubility in the absence of the catalyst metals, and produce at least partially water-insoluble compounds in combination with he metals. Effective precipitation with certain agents may require adjustment of the pH of the aqueous extract stream. Determination of which precipitating agents require adjustment of the pH of the extract stream is easily ascertained by one of ordinary skill in the art.
Suitable precipitating agents effective in precipitation of at least one metal catalyst from the aqueous extract include, but are not limited to, acetylacetone and alkali metal salts of acetylacetonates such as sodium acetylacetonate monohydrate; and oxalic acid and alkali metal salts of oxalates such as sodium oxalate. Salts are generally preferred.
The concentration of precipitating agent in the aqueous extract effective to result in precipitation of metal catalysts may be empirically determined by one of ordinary skill in the art. In general, an effective concentration in the aqueous extract is in the range from about 0.1 percent by weight to about 30 percent by weight, and preferably in the range from about 0.1% percent by weight to about 1% percent by weight. A concentrated aqueous solution of the precipitating agent may be prepared and used for the precipitation.
In a particularly advantageous embodiment, two or more metals are precipitated from the aqueous extract serially, by adding the precipitant in stages. Thus, where the metal-precipitant salts have differing solubilities, the addition of a first portion of the precipitant results predominantly in the precipitation of the less soluble metal precipitant salt. Addition of a second portion of the precipitating agent results in the precipitation of the more soluble metal-precipitant salt, and so on. A filtration or other solid-liquid separation process suffices to separate the first precipitate from the filtrate before the next precipitation is performed. As shown in Example 1 below, treatment of an aqueous mixture of palladium and cobalt with a limited quantity of sodium acetylacetonate, follow
General Electric Company
Griffin Steven P.
Ildebrando Christina
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