High surface area alumina solid

Details High surface area alumina solid High surface area alumina solid

1998-07-13

2001-05-29

Page, Thurman K. (Department: 1615)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Particulate form

C424S682000, C424SDIG001, C423S625000, C502S320000, C502S418000

Reexamination Certificate

active

06238701

ABSTRACT:

The present invention relates to a high specific surface area alumina solid, to a process for preparing it and to the use of particular molecular nanosystems as templates.
The preparation of alumina solids is known per se. Processes currently in industrial use are surveyed in Ullmann's Encycl. Tech. Chem., 5th ed. 1997, pp. 561-562, and in Winnacker, Kuchler, 4th edition, 1983 vol. 3, pp. 2-41.
Alumina thus prepared has a specific surface area in the range from 100 to 400 m
2
/g and pore diameters of from 2 to 5 nm, with large-pore aluminas generally having smaller surface areas. Such large-pore aluminas have a broad pore size distribution up to 10 nm.
Mesoporous oxides have likewise been described, for example in DE-A 44 07 326 and DE-A 195 43 638. According to these references, mesoporous oxides are prepared by adding a cationic, anionic or nonionic surfactant as a structure-directing reagent, or template, to the oxide precursors (monomers or oligomers) in the course of the polycondensation process to give an inorganic oxide. According to these references, the actual synthesis is followed by thermal removal of the template surfactants, for example by calcining in air at from 350 to 600° C., giving rise to a mesoporous, purely inorganic oxide.
“Mesoporous” means that the diameter of the pores in the solid is from about 2 to about 50 mn.
The pores of prior art mesoporous oxides are predominantly confined to the range around 2 nm or so.
However, oxide solids which have larger pores and which are inexpensive to produce are desirable for some applications, for example for use as heterogeneous catalysts, to optimize mass transfer in the reaction. This aim is achieved with some of the commercially available aluminas which, however, have broad pore diameter distributions and small specific surface areas. Furthermore, heat treatment may lead to the formation of various crystalline alumina phases (eg. &ggr;-Al
2
O
3
or, at even higher temperatures, &agr;-Al
2
O
3
) some of which have inherent catalytic properties such as Lewis or Broensted acidity and therefore have an undesirable effect on the reaction to be catalyzed.
It is an object of the present invention to provide an alumina solid which is suitable for a multiplicity of applications, in particular for use as catalyst or catalyst support, and a process for preparing this solid in an economically favorable, i.e. inexpensive, way.
We have found that, surprisingly, this object is achieved by using a dendrimeric molecular nanosystem as template in the preparation of the alumina solid.
The present invention accordingly provides a process for preparing an alumina solid, which comprises the step of contacting in a liquid medium at least one alumina precursor with at least one template comprising a dendrimeric molecular nanosystem or a mixture of two or more thereof.
This invention further provides an alumina solid obtainable by a process comprising the step of contacting in a liquid medium at least one alumina precursor with at least one template comprising a dendrimeric molecular nanosystem or a mixture of two or more thereof.


REFERENCES:
patent: 4871779 (1989-10-01), Killat et al.
patent: 814059 (1997-12-01), None
patent: 2316941 (1998-03-01), None
patent: 2316941 (1998-11-01), None
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Bagshaw et al.,Mesoporous Alumina Molecular Sieves,Angewandte Chemie, Int. Ed., 35, No. 19, 1996, 1102-5.
Mitsunori et al.,Chem. Comm.,1996, pp. 769-770.
Derwent Abstract 92-386258 (JP 04 285081, Oct. 9, 1992).
Stein et al.,J. of Porous Materials,3, 1996, pp. 83-92.
Goltner et al.,Advanced Materials,vol. 9, No. 5, Apr. 1997, pp. 431-436.

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