Organic compounds -- part of the class 532-570 series – Organic compounds – Carbonate esters
Reexamination Certificate
1999-08-27
2001-01-30
Ambrose, Michael G. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbonate esters
C558S271000, C558S272000, C558S273000, C502S304000, C502S331000
Reexamination Certificate
active
06180812
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the preparation of diaryl carbonates by oxidative carbonylation. More particularly, it relates to the improvement of diaryl 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.
A further development in the carbonylation reaction, including the use of compounds of other metals such as lead or cerium as cocatalysts, is disclosed in various patents including 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.
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. It has been discovered, however, that substitution of such compounds as sodium bromide normally results in the isolation of the desired diaryl carbonate in low or insignificant yield.
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.
In U.S. Pat. Nos. 5,543,547 and 5,726,340, the use of carbonylation catalyst systems including palladium or an analogous metal, various cocatalytic metals which may include cerium, lead or cobalt, and an alkali metal or quaternary ammonium bromide is disclosed. Japanese Kokai 10/316,627 discloses a similar process in which the cocatalyst is a manganese or lead compound and a carboxylic acid amide or alkylurea is also present.
The use of a specific amide, N-methylpyrrolidone (hereinafter sometimes “NMP”), in a system employing a cobalt cocatalyst and, as an organic cocatalyst, a terpyridine or the like is disclosed in U.S. Pat. No. 5,760,272. The sole disclosed function of the NMP is to improve the selectivity to the formation of diaryl carbonate, as opposed to by-products such as biphenols. Further study of this system has revealed that it affords no improvement in diaryl carbonate yield defined in terms of “turnover number”; i.e., the number of moles of diaryl carbonate formed per gram-atom of Group VIII catalytic metal present. This is contrary to the suggestion in the Japanese Kokai, which clearly teaches an improvement in yield.
It is of interest, therefore, to develop catalyst systems which include an inexpensive halide compound and which can efficiently produce diaryl carbonates.
SUMMARY OF THE INVENTION
The present invention provides a method for preparing diaryl carbonates which includes, a relatively inexpensive halide, a promoter compound which maximizes the effectiveness of said halide and a metal-containing cocatalyst. Also provided is a catalyst composition 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,
(C) at least one carboxylic acid amide, and
(D) at least one cocatalyst which is a compound of:
copper,
titanium in combination with zinc, copper or lead, or
cerium in combination with lead or manganese.
Another aspect of the invention is catalyst compositions comprising components A, B, C and D 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 are oxygen and carbon monoxide, which 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, nitriles, 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. 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 carboxylic acid amide, preferably a fully substituted amide; that is, one containing no NH groups including the amide nitrogen. It may be an aliphatic, aromatic or heterocyclic amide. Illustrative amides are dimethylformamide, dimethylacetamide (hereinafter sometimes “DMA”), dimethylbenzamide and NMP. Particularly preferred are NMP and DMA.
Component D is at least one cocatalyst which is a compound of copper, of a titanium-zinc, titanium-copper or titanium-lead mixture, or of a cerium-lead or cerium-manganese mixture.
Examples of lead compounds which may be employed are lead oxides such as PbO and Pb
3
O
4
; inorganic lead salts such as lead(II) nitrate; lead carboxylates such as lead(II) acetate and lead(II)propionate; lead alkoxides and aryloxides such as lead(II) methoxide and lead(II) phenoxide; and lead salts of &bgr;-diketones such as lead(II) 2,4-pentanedionate. Mixtures of the aforementioned lead compounds may also be employed. The preferred lead compounds are lead(II) oxide, lead
Johnson Bruce Fletcher
Pressman Eric James
Shalyaev Kirill Vladimirovich
Soloveichik Grigorii Lev
Ambrose Michael G.
General Electric Company
Johnson Noreen C.
Stoner Douglas E.
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