Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Halogen or compound containing same
Reexamination Certificate
1996-03-29
2003-04-15
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Halogen or compound containing same
C502S308000, C502S309000, C502S311000, C502S318000, C502S321000, C502S324000, C502S330000, C502S345000, C502S350000, C502S353000, C558S270000, C558S271000, C558S274000, C558S275000
Reexamination Certificate
active
06548445
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to supported catalysts containing a platinum metal and their use in processes for preparing diaryl carbonates by reaction of aromatic hydroxy compounds with carbon monoxide and oxygen, which are characterized in that the supported catalysts contain at least one cocatalyst in addition to the platinum metal.
2. Description of the Related Art
It is known that organic carbonates can be prepared by oxidative reaction of aromatic hydroxy compounds with carbon monoxide in the presence of a noble metal catalyst (German Offenlegungsschrift 28 15 512). The noble metal preferably used is palladium. In addition, a cocatalyst (e.g. manganese or cobalt salts), a base, a quaternary salt, various quinones or hydroquinones and desiccants can be used. The reaction can be carried out in a solvent, preferably methylene chloride.
For economically carrying out this process, not only the activity and the selectivity but also the effective recovery of the noble metal catalyst are of decisive importance: for one thing, the noble metal catalyst represents a considerable cost factor. Losses of noble metal catalyst have to be replaced at high cost. Furthermore, no residues of noble metal catalyst may remain in the product. For the process of oxidative carbonylation of aromatic hydroxy compounds to give diaryl carbonates, the economical and efficient recovery of homogeneous catalysts has hitherto not been described. A noble metal catalyst can be separated from a liquid reaction mixture with little effort, e.g. by filtration or centrifugation, if heterogeneous catalysts, e.g. supported catalysts, are used.
For preparing supported catalysts, suitable materials are known. Depending on the type of process, use is made of supports having a high internal surface area, for example aluminium oxide, magnesium oxide, activated carbon or silicon dioxide having more than 50 m
2
of surface area per gram, supports having surface areas around 5 m
2
/g and correspondingly larger pore radii, for example carbon black, titanium dioxide, iron oxide or zinc oxide, or coarse-grained supports, for example silicon carbide and corundum (Ullmanns Enzyklopädie der technischen Chemie, 3rd edition, Berlin/Munich 1957, Volume 9, p. 263 ff). Essentially, it is possible to use both synthetic materials such as activated aluminium oxides, silica gels, silicates, titanium dioxides or activated carbons and also materials from natural sources, for example pumice, kaolin, bleaching earths, bauxites, bentonites, kieselguhr, asbestos or zeolites. In EP 572 980, EP 503 581 and EP 614 876, use is made of supported noble metal catalysts containing 5% of palladium on carbon supports. However, according to our own studies, such supported catalysts give only very unsatisfactory conversions, if any, so that these too are not suitable for an economical process. In JP 01/165 551 (cited according to C.A. 112 (1990), 76618j) it is stated that, for the preparation of aromatic carbonates, palladium or palladium compounds such as palladium acetylacetonate can be used in combination with alkali metal (alkaline earth metal) iodides or onium iodides such as tetrabutylammonium iodide and at least one zeolite. JP 04/257 546 and JP 04/261 142 describe, in one example each, a supported catalyst for preparing aromatic carbonates in which granulated silicon carbide is used as support material for a supported catalyst in a distillation column. Although the relevant examples are carried out under drastic conditions (high pressure, high temperature), this catalyst makes possible only very low space-time yields. These low space-time yields make economical preparation of aromatic carbonates using such supported catalysts impossible.
Up to now, there is therefore no supported catalyst available by means of which diaryl carbonates can be prepared economically and efficiently by reaction of an aromatic hydroxy compound with carbon monoxide and oxygen. It was therefore an object of the invention to find a supported catalyst having high activity and selectivity which allows the economically efficient preparation of diaryl carbonates by reaction of an aromatic hydroxy compound with carbon monoxide and oxygen.
SUMMARY OF THE INVENTION
It has now been found that the above disadvantages can be overcome if use is made of supported platinum metal catalysts which contain at least one cocatalyst in addition to the platinum metal. The catalysts comprising platinum metal and at least one cocatalyst on a support are used according to the invention as powders, pellets or binder-containing extrudates. Suitable binders are, for example, SiO
2
, Al
2
O
3
or clay minerals. The binder contents can be varied within a wide range, for example from 0.5 to 99.5% by weight, based on the total weight of the support.
The supported catalysts of the invention contain, in the reaction-ready state, (i) a platinum metal, a platinum metal halide or a complex containing a platinum metal halide, or a compound which can be converted under the reaction conditions into a platinum metal, a platinum metal halide or a complex containing a platinum metal halide, in an amount of 0.01-15% by weight, preferably 0.05-10% by weight, calculated as platinum metal and based on the total weight of the catalyst, and (ii) a metal compound acting as cocatalyst from groups IB, IIB, IIIA, IIIB, IVA, IVB, VB, VIB, VIIB, the iron group (atomic numbers 26-28) or the rare earth metals (atomic numbers 58-71) of the Periodic Table of the Elements (Mendeleev) in an amount of 0.01-15% by weight, preferably 0.05-10% by weight, calculated as metal and based on the total weight of the catalyst.
Such catalysts are in the form of heterogeneously catalytic systems and thus make it easier to separate the reaction product from the expensive platinum metal, its compounds and the cocatalyst.
The invention further provides a process for preparing an aromatic carbonate of the formula
R—O—CO—O—R (I),
where
R is substituted or unsubstituted C
6
-C
12
-aryl, preferably substituted or unsubstituted phenyl, particularly preferably unsubstituted phenyl,
by reaction of an aromatic hydroxy compound of the formula
R—O—H (II),
where R is as defined above,
with carbon monoxide and oxygen in the presence of a quaternary ammonium or phosphonium salt and a base at from 30 to 200° C., preferably 30-150° C., particularly preferably from 40 to 120° C., and at a pressure of from 1 to 150 bar, preferably 2-50 bar, particularly preferably from 5 to 25 bar, which is characterized in that use is made of supported platinum metal catalysts which contain one or more cocatalysts of the above-described type and amount in addition to the platinum metal.
DETAILED DESCRIPTION OF THE INVENTION
For the example of the formation of diphenyl carbonate, the process of the invention can be represented in terms of formulae as follows:
2C
6
H
5
—OH+CO+½O
2
→(C
6
H
5
O)
2
CO+H
2
O
Catalyst supports suitable for use according to the invention are all industrially customary catalyst supports, for example those based on carbon, element oxides, element carbides or element salts in various use forms. Examples of carbon-containing supports are coke, graphite, carbon black or activated carbon. Examples of element oxide catalyst supports are SiO
2
(natural or synthetic silicas, quartz), Al
2
O
3
(&agr;-, &ggr;-Al
2
O
3
), aluminas, natural and synthetic aluminosilicates (zeolites), TiO
2
(rutile, anatase), ZrO
2
or ZnO. Examples of element carbides and salts are SiC, AlPO
4
, BaSO
4
, CaCO
3
, etc. They can be used either as chemically uniform pure substances or in admixture. Catalyst supports suitable for use according to the invention can be either in the form of pieces or as pulverulent materials. If the supported catalyst is arranged in a fixed bed, the support is preferably used as shaped bodies, e.g. as spheres, cylinders, rods, hollow cylinders, rings, etc. If desired, catalyst supports can be further modified by extrusion, pelletizing, optionally with
Buysch Hans-Josef
Hesse Carsten
Jentsch Jörg-Dietrich
Rechner Johann
Zirngiebl Eberhard
Bayer Aktiengesellschaft
Bell Mark L.
Hailey Patricia L.
Norris & McLaughlin & Marcus
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