Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1998-12-14
1999-12-28
Trinh, Ba K.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
502 66, 502242, 502243, 502261, 502263, C07D30106, B01J 2116, B01J 2352, B01J 2366, B01J 2904
Patent
active
060083891
DESCRIPTION:
BRIEF SUMMARY
Oxidation catalyst and preparation of epoxides from olefins, hydrogen and oxygen using the oxidation catalyst
The present invention relates to a novel oxidation catalyst based on titanium silicalites or vanadium silicalites having a zeolite structure and containing noble metals, and a process for the preparation of epoxides from olefins, hydrogen and oxygen using this oxidation catalyst.
Oxidation catalysts containing noble metals and based on titanium silicalites or vanadium silicalites having a zeolite structure and a process for the preparation of epoxides from olefins, hydrogen and oxygen using these oxidation catalysts are disclosed in WO-A 96/02323. There, the catalysts are used in the form of crystalline powder.
However, such oxidation catalysts of the prior art have disadvantages. When unmolded epoxidation catalysts are used, they are too fine-particled and therefore give rise to mechanical problems, for example when they are being separated off.
It is an object of the present invention to provide epoxidation catalysts which no longer have the disadvantages of the prior art.
We have found that this object is achieved by an oxidation catalyst based on titanium silicalites or vanadium silicalites having a zeolite structure and containing from 0.01 to 30% by weight of one or more noble metals selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, platinum, rhenium, gold and silver, wherein the oxidation catalyst has been molded by a compacting shaping process.
Compacting shaping processes which may be used are in principle all methods for appropriate shaping, such as those which are usual for catalysts. Processes in which the shaping is effected by extrusion in conventional extruders, for example to give extrudates having a diameter of, usually, from 1 to 10 mm, in particular from 2 to 5 mm, are preferred. If binders and/or assistants are required, the extrusion is advantageously preceded by a mixing or kneading process. If necessary, the extrusion may be followed by a calcination step. The extrudates obtained are, if desired, comminuted, preferably to give granules or chips having a particle diameter of from 0.5 to 5 mm, in particular from 0.5 to 2 mm. These granules or these chips and also catalyst moldings produced by other methods contain virtually no particles finer than those having a minimum particle diameter of 0.5 mm.
In a preferred embodiment, the novel molded oxidation catalyst contains up to 10% by weight, based on the total mass of the catalyst, of a binder. Particularly preferred binder contents are from 0.1 to 7, in particular from 1 to 5, % by weight. Suitable binders are in principle all compounds used for such purposes; compounds, in particular oxides, of silicon, of aluminum, of boron, of phosphorus, of zirconium and/or of titanium are preferred. Silica is of particular interest as a binder, and the SiO.sub.2 may be introduced into the shaping step in the form of silica sol or in the form of tetraalkoxysilanes. Oxides of magnesium and of beryllium and clays, for example montmorillonites, kaolins, bentonites, halloysites, dickites, nacrites and ananxites, may also be used as binders.
Examples of assistants for the compacting shaping processes are extrusion assistants, a conventional extrusion assistant being methylcellulose. Such agents are, as a rule, completely combusted in a downstream calcination step.
The molded oxidation catalysts prepared in this manner have a high mass-specific activity and hardness and abrasion resistance sufficient for all reaction procedures and reactor types.
The molded oxidation catalysts are based on titanium silicalites or vanadium silicalites having a zeolite structure. It is known that zeolites are crystalline aluminosilicates having ordered channel and cage structures whose pore orifices are in the range of micropores, which are smaller than 0.9 nm. The network of such zeolites is composed of SiO.sub.4 and AlO.sub.4 tetrahedra, which are linked via common oxygen bridges. A review of the known structures is given, for e
Grosch Georg Heinrich
Muller Ulrich
Rieber Norbert
Schulz Michael
Wurz Harald
BASF - Aktiengesellschaft
Trinh Ba K.
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