Organic compounds -- part of the class 532-570 series – Organic compounds – Carbonate esters
Reexamination Certificate
2000-02-11
2001-06-05
Lambkin, Deborah C. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbonate esters
Reexamination Certificate
active
06242632
ABSTRACT:
The present invention relates to platinum metal-containing supported catalysts in which the supports contain mixed oxides of metals, transition metals and semiconductor elements, which can act as redox catalysts under the reaction conditions and which have been prepared in a sol-gel process and use of the supported catalysts in a process for preparing diaryl carbonates by reacting aromatic hydroxy compounds with carbon monoxide and oxygen.
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 (DE-OS 28 15 512). Palladium is preferably used as the noble metal. In addition a co-catalyst (e.g. manganese or cobalt salts), a base, a quaternary salt, a variety of quinones or hydroquinones and a drying agent may also be used. The procedure may be performed in a solvent, preferably in methylene chloride.
In order to perform this process in an economic manner, effective recovery of the noble metal catalyst is a critical factor, in addition to the activity and selectivity of the catalyst. On the one hand the noble metal catalyst represents a large cost factor. Losses of noble metal catalyst have to be replaced at great cost. On the other hand no residues of the noble metal catalyst should remain in the product. The economic and efficient recovery of homogeneous catalysts for the process of oxidative carbonylation of aromatic hydroxy compounds to give diaryl carbonates has not hitherto been described. The separation of a noble metal catalyst from a liquid reaction mixture, e.g. by filtering or centrifuging, can be performed at low cost if heterogeneous supported catalysts are used.
In EP-A 572 980, EP-A 503 581 and EP-A 614 876 noble metal supported catalysts are used which contain 5% palladium on carbon supports. However, these types of supported catalysts produce only very unsatisfactory conversions or even none at all, so that these are also unsuitable for an economically viable process.
JP-A 01/165 551 (cited in accordance with C.A. 112:76618j (1990)) describes using palladium or palladium compounds such as palladium acetylacetonate, in combination with alkali metal or alkaline earth metal iodides or ‘onium’ iodides, such as tetrabutylammonium iodide, and at least one zeolite to prepare aromatic carbonates.
JP-A 04/257 546 and JP-A 04/261 142 each describe an example of a supported catalyst for preparing aromatic carbonates in which silicon carbide granules are used as the support material for a supported catalyst in a distillation column. Although drastic conditions (high pressure, high temperature) are used in the relevant examples, these catalysts produce only very low space-time yields. These low space-time yields make the economic production of aromatic carbonates with this type of supported catalyst impossible.
EP-A 736 324 describes the preparation of diaryl carbonates with heterogeneous catalysts which contain a platinum metal, preferably palladium, and a co-catalytic metal compound, preferably a metal from the group Mn, Cu, Co, Ce and Mo. When preparing the catalysts the co-catalytic metals are applied to a support.
EP-A 736 325 describes the preparation of diaryl carbonates with heterogeneous catalysts which contain a platinum metal, preferably palladium, on a support which consists of a metal oxide in which the metal may exist in several valency states.
Although these supported catalysts enable the preparation of aromatic carbonates for the first time, a further increase in activity is desirable from an economic point of view.
It has now been found that higher catalyst activities can be obtained if platinum metal-containing supported catalysts in which the support contains mixed oxides e.g. of V, Mn, Ti, Cu, La, the rare-earth metals and mixtures thereof which act as redox catalysts under the reaction conditions, which have been prepared in a sol-gel process and which contain platinum metals are used as catalysts.
The invention provides catalysts which contain
(i) an oxide of the elements silicon, aluminium, titanium, zirconium or a mixture of oxides of these elements,
(ii) one or more co-catalytic metal oxides from groups 4, 5, 6, 7, 11, 12, 13, 14, the iron group (atomic numbers 26 to 28) or the rare-earth metals (atomic numbers 58 to 71) in the periodic system of the elements in accordance with the new IUPAC nomenclature, and
(iii) one or more platinum metals or one or more compounds of platinum metals (atomic numbers 44 to 46 and 77 and 78) in an amount 0.01 to 15 wt. %, calculated as platinum metal and with respect to the total weight of catalyst,
which are obtained by preparing a gel from one or more suitable precursor(s) of the components mentioned under (i) and (ii), ageing, drying and optionally annealing the gel, shaping the mixed metal oxide obtained in this way and then applying the platinum metal component (iii) to the mixed metal oxide.
Supports according to the invention probably act like a separately added co-catalyst, but they avoid all disadvantages of separately added co-catalysts such as mixing with the reaction product and thus contaminating it. In accordance with this hypothesis, all the metals mentioned are those which can occur in several valency states. As a result of the special method of preparation, mixed oxides according to the invention are obtained which produce particularly active catalysts as compared with the prior art. This is particularly surprising since the activity of known catalysts is only very slightly affected by the method of preparation of the support.
Catalysts according to the invention contain, when ready to react
(i) an oxide of the elements silicon, aluminium, titanium, zirconium or a mixture of oxides of these elements,
(ii) one or more co-catalytic metal oxides of the groups 4, 5, 6, 7, 11, 12, 13, 14, the iron group (atomic numbers 26 to 28) or the rare-earth metals (atomic numbers 58 to 71) in the periodic system of the elements (IUPAC, new), and
(iii) one or more platinum metals or one or more compounds of platinum metals (atomic numbers 44 to 46 and 77 and 78) in an amount 0.01 to 15 wt. %, preferably 0.05 to 10 wt. %, calculated as platinum metal and with respect to the total weight of catalyst.
Catalysts according to the invention are prepared by preparing a gel from one or more suitable precursor(s) of the components mentioned under (i) and one or more suitable precursor(s) of the components mentioned under (ii), ageing the gel, drying and optionally annealing the gel, making the mixed metal oxide obtained into the desired form, e.g. powder, granules, extrudate, spheres, cylinders, hollow rings, using methods known to a person skilled in the art, and then applying the platinum metal components to the catalyst supports being used according to the invention using methods basically known to a person skilled in the art, such as, for example, soaking, adsorption, immersion, spraying, impregnation and ion exchange.
The mixed metal oxide supports are used according to the invention as powders, tablets or binder-containing extrudates. Suitable binders are e.g. SiO
2
, Al
2
O
3
or aluminas. The concentration of binder may be varied over a wide range, for example 0.5 to 99.5 wt. %, with respect to the total weight of support. The mixed metal oxide may also be applied as a layer on an inert material (wash coat).
The gel according to the invention can be prepared by almost any known method. Methods which are known for preparing mixed oxides based on a gel are preferably used. This includes, for example, the hydrolysis of one or more metal alkoxides and/or hydrolysable metal compounds under acid, neutral or basic conditions in suitable solvents at temperatures of 0° C. to 200° C. In this case mixtures of different precursors of one or more elements may also be used.
Suitable precursors of silicon dioxide are alkoxides of silicon such as, for example, tetraethoxysilane, tetramethoxysilane.
Suitable precursors of aluminium oxide are lower alkoxides such as trimethoxyaluminium, triethoxyaluminium, tri-n-propoxyalumini
Hesse Carsten
Notheis Ulrich
Rechner Johann
Bayer Aktiengesellschaft
Gil Joseph C.
Lambkin Deborah C.
Preis Aron
LandOfFree
Supported catalysts containing a platinum group metal and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Supported catalysts containing a platinum group metal and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Supported catalysts containing a platinum group metal and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2444163