Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2003-01-10
2004-08-03
Solola, Taofiq (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C502S243000
Reexamination Certificate
active
06770765
ABSTRACT:
FIELD OF THE INVENTION
The present invention provides hydro-oxidation catalysts, for the oxidation of hydrocarbons, containing an organic-inorganic hybrid material as well as gold particles and/or silver particles, a process for the production thereof, and methods of use thereof as a catalyst.
BACKGROUND OF THE INVENTION
Akylene oxides such as propene oxide, for example, can be produced from alkenes such as propene. In this procedure, alkenes are reacted, in the presence of catalysts, with oxygen and with a reducing agent, e.g. hydrogen. This process is termed a hydro-oxidation process and the catalysts used therein are termed hydro-oxidation catalysts (abbreviated herein: HO catalysts).
Purely inorganic catalysts that contain titanium and gold are known for the partial oxidation of hydrocarbons in the presence of oxygen and hydrogen. Catalysts of this type are disclosed, for example, in EP-A 0 709 360, EP-A 0 876 215, EP-A 0 827 779, WO 98/00414, WO 99/43431 and WO 99/52883.
Such catalysts are mainly powdered catalysts produced by multi-stage processes. Suitable powdered support materials, which are generally based on silicon oxide, are impregnated with a titanium precursor, washed, dried and converted in a subsequent process step into insoluble gold hydroxides in the liquid phase by means of gold precipitation by deposition precipitation (soluble gold precursors are converted into insoluble gold hydroxides, by changing the pH from acidic to basic. This means that gold hydroxides are precipitated on the support surface) with gold precursors at a controlled pH.
These so-called precursors are precursor compounds (salts and other compounds).
The powdered material which contains the Ti and Au and which is obtained in this manner cannot yet be used in a fixed bed reactor without a molding step.
Oxidation catalysts which contain noble metals and which are based on organic-inorganic hybrid materials, and a process of producing epoxides from olefins, oxygen and hydrogen using these oxidation catalysts, are known from WO 01/41921. Powdered catalysts are used. Organic-inorganic hybrid materials, which contain titanium are produced by a sol-gel process. The gold content of this hybrid process is imparted in a subsequent impregnation step. This impregnation is termed incipient wetness. Incipient wetness is an impregnation in which an accurately determined amount of solvent is used which corresponds to the pore volume of the support. This gives rise to a sponge effect, in which the support often remains dry on a macroscopic scale.
Similar oxidation catalysts containing noble metals and which are based on organic-inorganic hybrid materials are described in DE-A 101 07 777, but differ from the systems described above in that noble metal particles are deposited on to the finished hybrid materials by spray-drying, namely in a subsequent step comprising a sol-gel process which includes gel work-up. Catalysts which range in size from powders to pellets are obtained (molding size <2 mm) depending on the process.
DE-A 100 23 717 describes oxidation catalysts based on organic-inorganic hybrid materials which have a content of noble metals and which can be used for the production of epoxides from olefins. In a subsequent step, these powdered catalysts are formed into moldings, such as extrudates, granules, pellets, etc.
As an alternative to the molding process described in DE-A 100 23 717 (conversion of organic-inorganic hybrid materials which contain gold and/or silver into moldings using binders, fillers and molding apparatuses such as extrusion presses, extruders, etc.), a route to HO catalysts is known in which an organic-inorganic hybrid material which does not contain noble metals is deposited on the inert moldings by impregnation, and the noble metal is deposited on the impregnated molding in a subsequent step.
All the processes published heretofore have the disadvantage that the catalysts disclosed therein are produced by multi-stage syntheses, and are therefore associated with high manufacturing costs.
For industrial processes, it is desirable to develop catalysts which achieve service lives of industrial interest, whilst exhibiting excellent selectivities and high productivities. Moreover, a pressure drop across the catalyst bed that is as low as possible is desirable. In order to produce catalysts on an industrial scale (a tonnage scale), the process steps for the preparation of the catalysts should be as reproducible and as simple as possible. To achieve an economic process, the cost of catalyst production should be very low.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides catalysts exhibiting low pressure drops for industrial processes, which provide improved selectivities and productivities compared with the prior art.
The present invention further provides a process of producing these highly active catalysts.
The present invention also provides a process of producing these highly active catalysts which is as reproducible as possible.
The highly active catalysts of the present invention have a high mechanical strength.
The present invention yet further provides a process of catalyst production, the cost of which is as low as possible. This is accomplished by having only a few preparation steps and the use of simple apparatus.
The present invention still further provides a catalyst for the oxidation of hydrocarbons.
The present invention greatly reduces or eliminates the disadvantages of known powdered catalysts (high pressure drop in tubular reactors, more rapid deactivation as a result of elevated local catalyst concentration).
The present invention still further provides a technologically simple, gas phase hydro-oxidation process for the selective oxidation of hydrocarbons with a gaseous oxidizing agent and in the presence of a reducing agent on said catalysts, which results in high yields and low costs whilst achieving high catalyst productivities, very high selectivities and catalyst service lives of industrial interest.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be described for purposes of illustration and not limitation.
The present invention provides a process for producing a catalyst comprising the provision of a support and impregnation of the support with an organic-inorganic hybrid sol which contains titanium and which contains gold and/or silver.
The process may preferably include modifying the surface of the catalyst with silicon alkyl compounds, silicon aryl compounds and/or SiH compounds.
In this respect, the support may preferably be selected from the group consisting of oxides of silicon, oxides of aluminium, oxides of zirconium, oxides of titanium, oxides of boron, zeolites, clays, mixed oxides of the aforementioned oxides, carbon, activated carbon, carbon black, graphite, monoliths, knitted fabrics, cordierite monoliths, ceramic foams, alkali carbonates, alkaline earth carbonates, carbides, silicon carbide, silicon nitride, metals, glasses and mixtures thereof.
More preferably, the support is selected from the group consisting of alumina, silicon oxide, silicon carbide, carbon and a cordierite monolith.
Most preferably, the support is &agr;-alumina or silicon carbide.
The process may also preferably include an annealing step at temperatures in the range from 100-1000° C., particularly from 200 to 600° C.
The catalyst of the present invention comprises a support, an organic-inorganic hybrid material which is formed from the organic-inorganic hybrid sol, titanium in chemically bound form, and gold particles and/or silver particles.
A preferred organic-inorganic hybrid material for the catalyst of the present invention is based on silicon oxide.
In this respect, the organic-inorganic hybrid material may preferably contain terminal and/or bridging organic groups on the silicon atoms of the organic-inorganic hybrid material.
The catalyst preferably contains gold and silver in the organic-inorganic hybrid material in an amount between 0.001 to 15% by weight.
More preferably, the content of gold in the organic-inorganic h
Dugal Markus
Heinen Marie-Therese
Schmitt Jörg
Wegener Gerhard
Weisbeck Markus
Bayer Aktiengesellschaft
Gil Joseph C.
Mrozinski, Jr. John E.
Solola Taofiq
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