Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Patent
1997-03-18
1999-08-10
Bell, Mark L.
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
502233, 502236, 502239, 502242, 502405, 502408, 502415, 501 12, 516111, B01J 2300, B01J 2000, B01J 1300, C03C 300
Patent
active
059358955
DESCRIPTION:
BRIEF SUMMARY
Processes are known according to which olefin oxides (epoxides) are manufactured by reacting corresponding olefins with organic hydroperoxides using certain heterogeneous catalysts. Suitable catalysts which are effective for this purpose are oxides or hydroxides of, for example, titanium or molybdenum, which are chemically combined with silicon oxides, e.g. silicon dioxide (silica). By treating such heterogeneous catalysts, e.g. titanium dioxide (titania) chemically combined with silica, with an organic silylating reagent, e.g. an organic halosilane, at elevated temperatures there is achieved according to U.S. Pat. Nos. 3,829,392 and 3,923,843 a better productivity, with the selectivity of the epoxidation being improved and the tendency of the organic hydroperoxide to decompose to undesired byproducts under the influence of the heterogeneous catalyst being reduced.
As is known, disadvantages of heterogeneous catalysts of the above type in comparison to homogeneous catalysts, e.g. molybdenum compounds, are the relatively low activity and somewhat lower selectivity. The known high reactivity of organic hydroperoxides, especially in the epoxidation of olefins, and the general tendency of these hydroperoxides to decompose in the presence of a variety of catalytic materials to undesired byproducts has motivated the search for more selective and more active catalysts for the epoxidation of olefins and also for other oxidations.
The object of the present invention was to provide silica-titania mixed oxide catalysts which on the one hand exhibit an increased activity in oxidations with organic hydroperoxides, especially in epoxidations of olefins, and on the other hand are at least equal to known catalysts with respect to selectivity and the stability of titanium in the solid matrix of the mixed metal oxides. In order to fulfill these goals efforts were made to achieve an intermixing of the silicon and titanium components, each being bridged via an oxygen atom, as atomically as possible, i.e. the provision of as many as possible bonds of the Si--O--Ti type in a highly cross-linked structure; a specific surface area which is as high as possible; a pore volume which is as large as possible; as well as not only a dispersion of the titanium which is as high as possible, but also its accessibility at the surface. These characteristics are of great significance for catalysis in the field of fine chemicals. In particular, a large pore volume is necessary in order that the relatively large molecules generally encountered in fine chemistry can enter into the porous catalyst.
It has surprisingly been found that the desired silica-titania mixed oxide catalysts can be manufactured by producing a sol under acidic or basic hydrolysis conditions from optionally pre-hydrolyzed silicon alkoxide and from titanium alkoxide, the hydrolyzability of which is reduced by chelate formation, gelling and ageing this sol, drying the thus-produced aged gel by extraction of the solvent used in the production of the sol and of the alcohol produced in the hydrolysis with super-critical carbon dioxide and, if desired, calcinating the aerogel resulting therefrom at temperatures up to 1000.degree. C. in a gas stream containing oxygen. The present invention is concerned with a thus-manufacturable catalyst, the respective process for the manufacture of the catalyst, and the use of such catalysts in the epoxidation of olefinically unsaturated compounds with organic hydroperoxides.
U.S. Pat. No. 4,176,089 teaches the preparation of mixed silica-titania materials, suitable as catalysts or catalyst supports, by mining silicon and titanium alkoxides and an organic diluent, adding the resulting premixed alkoxides to a hydrolysis medium of water and a solvent to form a silica-titania precipitate, separating this from the hydrolysis medium, drying and calcinating the precipitate and recovering the resulting high surface area, low bulk density silica-titania product. However, there is no disclosure in this U.S. patent specification of reducing the hydrolyzabi
REFERENCES:
patent: 3829392 (1974-08-01), Wulff
patent: 3923843 (1975-12-01), Wulff
patent: 4432956 (1984-02-01), Zarzycki et al.
patent: 4478987 (1984-10-01), Fanelli et al.
patent: 4550093 (1985-10-01), Fanelli et al.
patent: 4619908 (1986-10-01), Cheng et al.
patent: 4717708 (1988-01-01), Cheng et al.
patent: 5008219 (1991-04-01), Hara
patent: 5019146 (1991-05-01), Hara
patent: 5558849 (1996-09-01), Sharp
Baiker Alfons
Dutoit Dominique
Hutter Remo
Bell Mark L.
Hailey Patricia L.
Johnston George W.
Roche Vitamins Inc.
Tramaloni Dennis P.
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