Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
1999-11-17
2002-07-02
Griffin, Steven P. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S350000
Reexamination Certificate
active
06413905
ABSTRACT:
The present invention relates to supported catalysts made up of modified supports and an active component, their production and their use in the hydrogenation of unsaturated compounds.
Supported catalysts, in particular supported oxides, play an important role in catalysis. A study of adsorbed O
2
indicates that oxides supported on diamagnetic support materials are sometimes enriched in less electron-rich oxygen species such as O
2
−
and O
−
because their surface has only a low density of electron-donating centers. Since selective oxidation of organic molecules requires that only a limited amount of active O
2
is made available, numerous mixed and supported oxides are employed here. Since their surfaces also have various adsorption sites, the modification of supports by application of further components (hereinafter referred to as modifiers) enables activity and selectivity of the catalysts to be influenced over wide ranges.
The support materials can interact with the active metal. Such interactions of the metals with reducible oxides resulting from high reduction temperatures (over 700 K) are generally referred to as strong metal-support interactions (SMSI). A description of SMSI assumes that ions of the support oxide migrate to the surface of the reduced metal at high reduction temperatures. Such modifiers enable the activity of the catalyst in various reactions to be increased. The increased activity is generally attributed to the active component being highly dispersed. In addition, the catalysts have a high sintering and agglomeration stability.
Carturan, G. Chim. Int. (Milan) 65 (1983) 688, describes the hydrogenation of polyunsaturated C
18
-fatty acids using palladium catalysts. One of the catalysts used comprises a support of glass beads which are coated with TiO
2
. The TiO
2
is applied from an ethanolic Ti(OEt)
4
solution, followed by heating to 400° C. The modification of the support material is carried out here by pretreating the shaped body, namely the glass beads, with a precursor compound of the modifier.
Ryndin et al., Applied Catalysis, 63 (1990) 37 to 50, describe a study of the influence of group IVB ions on the adsorption and the catalytic properties as well as the dispersion of the active metal in the system Pd/SiO
2
. The catalyst system is produced from dehydrated SiO
2
and tetrabenzyltitanium, tetrabenzylzirconium or tetrabenzylhafnium and subsequent adsorption of allyl(cyclopentadienyl)palladium. During production of the catalyst, air is excluded completely. The synthesis of MeOH from CO and H
2
and the hydrogenation of benzene in the presence of the catalyst are studied.
EP-A 0 225 953 discloses catalysts comprising a metal alkoxide-modified support and a catalytically active metal of transition group VIII of the Periodic Table of the Elements. In the examples, the only support material used is &ggr;-Al
2
O
3
which has been modified with a metal alkoxide. The application of the catalytically active metals is carried out exclusively by impregnation with a solution of their chlorides or nitrates. The catalysts display increased activity in the disproportionation of alkenes, in a gas-phase process for preparing &agr;-substituted acrylate esters or methyl methacrylates, in processes for the selective hydrogenation of hydrocarbons having at least one alkene and one alkyne unit, where the alkyne is hydrogenated without hydrogenation of the alkene, and in a process for preparing methane from CO and H
2
.
K. Matsuo et al. Appl. Surf., pages 33, 34 (1998), 269-276, describe catalysts comprising a titanium-coated silica support in which metals of the Pt group are present as active component. The Ti/SiO
2
support can be produced by various methods:
a) Gas-phase hydrogenation of titanium alkoxides and adsorption on SiO
2
;
b) Pyrolysis of titanium alkoxides and adsorption on SiO
2
;
c) Adsorption of titanium colloids on SiO
2
.
These supports are impregnated with metals of the Pt group, in the case of palladium with PdCl
2
. The metal-support interactions (SMSI) are examined in the total oxidation of acetone. In these studies, it was found that only the catalyst produced by method a) is active. This makes it clear that the properties and the catalytic activity of the modified supported catalysts are influenced by the method by which they are produced.
It is an object of the present invention to provide a catalyst and a process for producing this catalyst, which catalyst has the active component highly dispersed, has a high sintering and agglomeration stability and is superior to the catalysts described in the prior art, especially for use in the hydrogenation of unsaturated compounds.
We have found that this object is achieved by a supported catalyst comprising a catalytically active metal and a support modified by application of modifiers to an inner support material. The catalyst of the invention is produced by applying the catalytically active metal in the form of its chloride-free dissolved amine complexes, acetylacetonate complexes or allyl complexes to the modified support.
In the supported catalysts of the present invention, the catalytically active metal is dispersed particularly finely and in a particularly stable fashion. Avoiding the use of chloride ions prevents adverse effects of the chloride ions on the dispersion and activity of the catalytically active metal.
For the purposes of the present invention, modifiers are components which are applied to supports and influence the activity and selectivity of the catalyst.
For the purposes of the present invention, an inner support material is the support component still to be modified. The support is composed of inner support material and modifier.
The inner support material is preferably pretreated thermally prior to application of the modifiers. The modification of the inner support material by the modifier is based on the hypothesis that a hydrolysis-sensitive modifier compound (the modifier precursor) added in excess to the inner support material reacts with the surface hydroxyl groups of the inner support material. The number of surface groups available for this can be controlled, according to E. F. Vansant, P. Van der Voort and K. C. Vrancken “Studies in Surface Science and Catalysis”, Vol. 93, Chapter 4, pages 79 to 88, Editors: B. Delmon and J. T. Yates, Elsevier, 1995 and Ralph K. Iler “The Chemistry of Silica”, pages 624 to 637, John Wiley & Sons, 1979, for the example of SiO
2
, by thermal pretreatment of the inner support material. The thermal pretreatment of the inner support material accordingly has a decisive influence on the properties of the catalyst.
The inner support material used is preferably a material selected from the group consisting of Al
2
O
3
, SiO
2
, TiO
2
, ZrO
2
, aluminosilicates, MgO and activated carbon which has been chemically modified by surface oxidation. Particular preference is given to using SiO
2
as inner support material.
The support material can be present in any form. Preference is given to powder, granules, extrudates, spheres, pellets or rings.
As modifier precursor, use is made of compounds comprising a metal of transition group IV, V, VI or VIII of the Periodic Table of the Elements. The modifier preferably comprises an element selected from the group consisting of Ti, Zr, Hf, V, Nb, Cr, Mo, W, Mn, Ta. Particular preference is given to using compounds of Ti, Zr, Nb, Ta as modifier.
The future modifiers are generally applied in the form (the precursor form) of their alkoxides, halides, oxalates or carboxylates. They are preferably applied in the form of their alkoxides. These should be hydrolysis-sensitive so that they can be converted into their oxides. Compounds selected from the group consisting of titanium tetraisopropoxide, titanium tetrachloride, zirconium bromide, zirconium isopropoxide, niobium(V) ethoxide, niobium(V) isopropoxide, niobium oxalate, niobium ammonium oxalate, tantalum chloride and tantalum ethoxide are particularly preferably used. Very particular preference is given to using titanium tetraisopropoxide and nio
Knözinger Helmut
Landes Helmut
Meyer Gerald
Schwab Ekkehard
BASF - Aktiengesellschaft
Griffin Steven P.
Ildebrando Christina
Keil & Weinkauf
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