Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
2000-05-26
2002-02-12
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C502S172000, C502S224000, C502S154000, C502S328000, C502S330000, C502S339000, C502S349000, C502S326000
Reexamination Certificate
active
06346500
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the preparation of diary carbonates by carbonylation. More particularly, it relates to the improvement of diary carbonate yield in the carbonylation reaction.
Diaryl carbonates are valuable intermediates for the preparation of polycarbonates by transesterification with bisphenols in the melt. This method of polycarbonate preparation has environmental advantages over methods which employ phosgene, a toxic gas, as a reagent and environmentally detrimental chlorinated aliphatic hydrocarbons such as methylene chloride as solvents.
Various methods for the preparation of diaryl carbonates by an oxidative carbonylation (hereinafter sometimes simply “carbonylation” for brevity) reaction of hydroxyaromatic compounds with carbon monoxide and oxygen have been disclosed. In general, the carbonylation reaction requires a rather complex catalyst. Reference is made, for example, to U.S. Pat. No. 4,187,242, in which the catalyst is a heavy Group VIII metal; i.e., a Group VIII metal having an atomic number of at least 44, said metals consisting of ruthenium, rhodium, palladium, osmium, iridium and platinum, or a complex thereof.
The production of carbonates may be improved by including a metal-based cocatalyst along with the heavy Group VIII metal catalyst. Although the identity of suitable metal-based cocatalysts will depend on specific reaction conditions including the identity of reactants and other members of the catalyst package, some general guidance can be found in U.S. Pat. Nos. 4,187,242 and 4,201,721.
A further development in the carbonylation reaction, including the use of specific lead compounds as cocatalysts, is disclosed in U.S. Pat. No. 5,498,789. Also required according to that patent is the use of quaternary ammonium or phosphonium halides, as illustrated by tetra-n-butylammonium bromide, as part of the catalyst package. Compounds characterized as inert solvents, such as toluene, diethyl ether, diphenyl ether and acetonitrile, can also be present.
The commercial viability of the carbonylation reaction would be greatly increased if a less expensive compound could be substituted for the quaternary ammonium or phosphonium halide. Substitution of such compounds as sodium bromide, however, result in the isolation of the desired diaryl carbonate in low or insignificant yield.
It is of interest, therefore, to develop catalyst systems which include an inexpensive halide compound and which can efficiently produce diaryl carbonates. Some such systems are known. Reference is made, for example, to Japanese Kokai 10/316,627, which discloses the use of palladium and a lead or manganese compound in combination with a halide such as sodium bromide and with an amide or alkylurea. U.S. Pat. No. 5,726,340 and Japanese Kokai 9/278,716 disclose similar systems in which the lead is combined with another metal and in which inert solvents such as those mentioned hereinabove may be present. The development of other systems employing relatively inexpensive halides, however, remains desirable.
SUMMARY OF THE INVENTION
The present invention provides a method for preparing diaryl carbonates which includes a relatively inexpensive halide and a compound which maximizes the effectiveness of said halide. Also provided are catalyst compositions useful in such a method.
In one of its aspects, the invention provides a method for preparing a diaryl carbonate which comprises contacting at least one hydroxyaromatic compound with oxygen and carbon monoxide in the presence of an amount effective for carbonylation of at least one catalytic material comprising:
(A) a Group VIII metal having an atomic number of at least 44 or a compound thereof,
(B) at least one alkali metal halide or alkaline earth metal halide, and
(C) at least one polyether.
Another aspect of the invention is catalyst compositions comprising components A, B and C as described above, and any reaction products thereof.
DETAILED DESCRIPTION PREFERRED EMBODIMENTS
Any hydroxyaromatic compound may be employed in the present invention. Monohydroxyaromatic compounds, such as phenol, the cresols, the xylenols and p-cumylphenol, are generally preferred with phenol being most preferred. The invention may, however, also be employed with dihydroxyaromatic compounds such as resorcinol, hydroquinone and 2,2-bis(4-hydroxyphenyl)propane or “bisphenol A”, whereupon the products are polycarbonate oligomers.
Other reagents in the method of this invention include oxygen and carbon monoxide, which can react with the phenol to form the desired diaryl carbonate. They may be employed in high purity form or diluted with another gas such as nitrogen, argon, carbon dioxide or hydrogen which has no negative effect on the reaction.
For the sake of brevity, the constituents of the catalyst system are defined as “components” irrespective of whether a reaction between said constituents occurs before or during the carbonylation reaction. Thus, the catalyst system may include said components and any reaction products thereof.
Component A of the catalyst system is one of the heavy Group VIII metals, preferably palladium, or a compound thereof. Thus, useful palladium materials include elemental palladium-containing entities such as palladium black, palladium/carbon, palladium/alumina and palladium/silica; palladium compounds such as palladium chloride, palladium bromide, palladium iodide, palladium sulfate, palladium nitrate, palladium acetate and palladium 2,4-pentanedionate; and palladium-containing complexes involving such compounds as carbon monoxide, amines, nitrites, phosphines and olefins. Preferred in many instances are palladium(II) salts of organic acids, most often C
2-6
aliphatic carboxylic acids, and palladium(II) salts of &bgr;-diketones. Palladium(II) acetate and palladium(II) 2,4-pentanedionate are generally most preferred. Palladium(II) acetylacetonate is also a suitable palladium source. Mixtures of the aforementioned palladium materials are also contemplated.
Component B is at least one alkali metal or alkaline earth metal halide, preferably a bromide such as lithium bromide, sodium bromide, potassium bromide, calcium bromide or magnesium bromide. Alkali metal bromides are especially preferred, with sodium bromide often being most preferred by reason of its particular suitability and relatively low cost.
Component C is at least one polyether; i.e., at least one compound containing two or more C—O—C linkages. The polyether is preferably free from hydroxy groups to maximize its desired activity and avoid competition with the hydroxyaromatic compound in the carbonylation reaction.
The polyether preferably contains two or more (O—C—C) units. The polyether may be “aliphatic” or mixed aliphatic-aromatic. As used in the identification of the polyether, the term “aliphatic” refers to the structures of hydrocarbon groups within the molecule, not to the overall structure of the molecule. Thus, “aliphatic polyether” includes heterocyclic polyether molecules containing aliphatic groups within their molecular structure. Suitable aliphatic polyethers include diethylene glycol dimethyl ether (hereinafter “diglyme”), triethylene glycol dimethyl ether (hereinafter “triglyme”), tetraethylene glycol dimethyl ether (hereinafter “tetraglyme”), polyethylene glycol dimethyl ether and crown ethers such as 15-crown-5 (1,4,7,10,13-pentaoxacyclopentadecane) and 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane). Illustrative mixed aliphatic-aromatic polyethers are diethylene glycol diphenyl ether and benzo-18-crown-6.
In a highly preferred embodiment of the invention, there is also present in the catalyst system (D) at least one cocatalyst which is a compound of a metal other than a heavy Group VIII metal. This metal is preferably one which is soluble in the liquid phase under the reaction conditions. Numerous other metal compounds are known in the art to be active as carbonylation cocatalysts, and any compound having such activity may be used according to the present invention provided an improvement in diphenyl carbonate production, usu
Johnson Bruce Fletcher
Pressman Eric James
Shalyaev Kirill Vladimirovich
Soloveichik Grigorii Lev
Bell Mark L.
General Electric Company
Hailey Patricia L.
Igraham Donald S.
Patel Ben P.
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