Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Patent
1998-07-06
2000-10-03
Griffin, Steven P.
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
502233, 423338, B01J 3100, B01J 2108, C01B 3312
Patent
active
061273066
DESCRIPTION:
BRIEF SUMMARY
The invention relates to organofunctionalized aerogels, to a process for their preparation, and to their use.
Aerogels are highly porous low-density materials, prepared by forming a gel and subsequently eliminating the liquid with preservation of the gel structure.
According to a narrow definition (see e.g. Gesser and Gaswami, Chem. Rev. 1989, 89, 767) the term aerogel is understood to refer to a material in which the liquid has been removed from the gel under supercritical conditions, whereas, when the gel is dried under subcritical conditions, the resulting product is called a xerogel, and when the liquid is eliminated from the frozen state by sublimation, the product is called a cryogel.
Aerogels within the meaning of the present invention comprise all these materials, and may also contain any gas besides air.
Because of their high porosity, aerogels have interesting physical properties which make them suitable for use, among other things, as heat insulating materials, acoustic materials, luminescent solar collectors, gas filters, catalysts or supporting materials.
For many of these applications, it is desirable to be able to modify the chemical properties of aerogels, e.g. through the incorporation of functional groups.
DE-A 40 02 287 describes functionalized inorganic xerogels. However, under the conditions of preparation indicated therein, no products having a gel structure are obtained, thus the products are not aerogels within the meaning of the present invention.
Aerogels etherified with amino alcohols are described in U.S. Pat. No. 5,270,027. However, such ether bridges do not have a particularly long storage stability, so that a gradual splitting-off of the organic groups takes place.
EP-A 0 629 442 discloses aerogels containing chelated transition metals as catalysts, and Cao and Hunt (Mat. Res. Soc. Symp. Proc. 1994, Vol. 346, 631) describe amino-functionalized aerogels.
Schubert et al. (Mat. Res. Soc. Symp. Proc. 1994, Vol. 348, 151) have synthesized aerogels containing methacryloxypropyl and glycidoxypropyl groups.
However for the above-mentioned fields of application, there continues to be a demand for additional organofunctionalized aerogels.
Surprisingly, it has now been found that aerogels having (pseudo)halogen, thio and phosphano functions on their inner surface can be prepared without destroying these functional groups or the gel structure during the course of the production process.
Hence the present invention relates to an aerogel which contains functional groups of formula (I), preferably 1 to 12, and, by particular preference, 2 to 3 carbon atoms; preference, Cl; pseudohalogen, preferably CN or SCN, SR.sup.1, PR.sup.2 R.sup.3, a dye residue or a metal complex residue; 22, preferably 1 to 12 carbon atoms, or an aryl group having 4 to 10 carbon atoms, and preferably phenyl (Ph) or naphthyl; represent a straight-chain or branched alkyl group having 1 to 22, and preferably 1 to 12, carbon atoms, or an aryl group containing 4 to 10 carbon atoms, and preferably phenyl (Ph) or naphthyl.
In general, the aerogels used are those based on metal oxides suitable for the sol-gel technology (see e.g. C. J. Brinker and G. W. Scherer, Sol-Gel Science, 1990, Chapters 2 and 3), such as Si, Al, Ti, Sn or Zr compounds, or those based on organic substances suitable for the sol-gel technology, such as melamine-formaldehyde condensates (U.S. Pat. No. 5,086,085) or resorcinol-formaldehyde condensates (U.S. Pat. No. 4,873,218). However, they can also be based on mixtures of the aforementioned materials. Used by preference are aerogels containing Si or Al compounds, particularly Si compounds; SiO.sub.2 aerogels are particularly preferred.
The aerogels according to the invention preferably contain the functional groups --Y--Z linked directly to the metal, semimetal or carbon component of the aerogel, i.e., for example, to Si, Al, Ti, Sn, Zr or C. As a result, the organic functional group is, preferably, not linked to the aerogel via an oxygen atom.
The aerogels of the invention can be prepared e.g. from mixt
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Husing Nicola
Schubert Ulrich
Donley Cynthia M
Griffin Steven P.
Hoechst Research and Technology Deutscland GmbH & Co. KG
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