Aerogel Supported Nanoparticles in Catalysis

Dedicated to the memory of Prof. Mardal Moreno-Manas 

Within the currently ubiquous nanoscience and nanotechnology efforts, the use of nanoparticles and nanostructured materials in catalysis appears as one of the most successful approaches [1]. It has been said that the most important drawback in nanoparticle appUcations is their tendency to aggregate and their dispersion in porous media has been shown to be a good way to prevent this. In this chapter a particularly interesting porous supporting material for nanoparticles, the aerogels, will be reviewed and their use in catalytical processes analyzed. 

The precursory gel of an aerogel, prior to the drying step, is usually obtained by a series of hydrolysis and condensation reactions of the initial reactants to form a sol. This complex process is affected by many parameters such as the nature and concentration of the alkoxide and the solvent, the water concentration, the temperature and the presence of add or base catalysts. AH will greatly influence the characteristics of the material obtained. For instance, the alkoxide concentration will define the 

Copyright 2008 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim 

Nanocomposite aerogels mainly consist as homogeneous dispersions of nanoparticles in an aerogel matrix. The preparation of nanocomposite aerogels can be 

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I 5 Aerogel Supported Nanoparticles in Catalysis 5.2.3.2 Methanol Oxidation... 

The preparation of nanocomposite aerogels made out of zero-valent metal or alloy nanoparticles in an insulating aerogel matrix has attracted a great deal of effort in view of the preparation of materials for catalysis, biomedicine, optoelectronics, and sensors. As it is the case for aU sol-gel nanocomposites, silica is by far the most investigated matrix for supporting metal/alloy nanoparticles, although alumina, titania, chromia, and polymer supports have also been proposed. 

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