Nanocluster heterogeneous catalysts

Many different topics are involved in the study of metallic nanoparticles and many fundamental issues can be present for example, which is the infiuence of the nanoparticle size, shape and composition on the chemical activity of heterogeneous catalysts Or, considering another problem, at what size does a small particle behave like the bulk material, for example, changing from an insulator to a semiconductor [9-12] An enormous amount of literature is published on metallic nanoclusters this review is focusing on the relevant problem concerning the characterization of metallic nanosized materials from the morphological and... 

Aiken, III, ID. Lin, Y., and Finke, R.G., A perspective on nanocluster catalysis polyoxonation and tetrabutylamonium stabilized Ir(> Vj0 nanocluster soluble heterogeneous catalysts, J. Mol. Catal. A,... 

Gold nanoclusters, luminescent properties, 12, 775 Gold nanoparticles, characteristics, 12, 495 -96 Gold-platinum clusters, as heterogeneous catalyst precursors,... 

Mori K, Hara T, Mizugaki T et al (2004) Hydroxyapatite-supported palladium nanoclusters A highly active heterogeneous catalyst for selective oxidation of alcohols by use of molecular oxygen. J Am Chem Soc 126(34) 10657-10666... 

Colloidal dispersions of metal nanoclusters usually work at rather low temperatures as homogeneous catalysts. On this point, metal nanoclusters are similar to enzymes and are often regarded as artificial enzymes. From the viewpoint of green chemistry (less energy, fewer by-products, more efficiency, more selectivity, etc.), enzymes are model industrial catalysts. Thus, metal nanoclusters may provide the means for industrial catalysts to step up from the present practical heterogeneous catalysts to more ideal and enzyme-like ones. 

Hara T, Kaneta T, Mori K, Mitsudome T, MizugaM T, Ebitani K, Kaneda K (2007) Magnetically recoverable heterogeneous catalyst palladium nanocluster supported on hydroxyapatite-encapsulated c-Fe203... 

Mori, K., Hara, T., Mizugaki, T., et al. (2004). Hydroxyapatite-Supported Palladium Nanoclusters A Highly Active Heterogeneous Catalyst for Selective Oxidation of Alcohols by Use of Molecular Oxygen, J. Am. Chem. Soc., 126, pp. 10657—10666. 

In the sixties of past century, a few patents issued to Bergbau Chemie [5,48,49] and to Mobil Oil [50-52], respectively described the use of CFPs as supports for catalytically active metal nanoclusters and as carriers for heterogenized metal complexes of catalytic relevance. For the latter catalysts the term hybrid phase catalysts later came into use [53,54], At that time coordination chemistry and organo-transition metal chemistry were in full development. Homogeneous transition metal catalysis was expected to grow in industrial relevance [54], but catalyst separation was generally a major problem for continuous processing. That is why the concept of hybrid catalysis became very popular in a short time [55]. 

This argument is confirmed by the study of CO pulse chemisorption by Biffis at al., mentioned above. In this piece of investigation, the authors prepared a 2% (w/w) palladium catalyst supported by Lewatit UCP 118, a macroreticular resin (nominal cld = 18 %) from Bayer. Its TEM characterization showed a remarkably heterogeneous distribution of the metal nanoclusters, which are apparently located close to the surface of the polymer nodules [62] (Figure 9). 

From the discussion in the previous sections, it is apparent that whatever the morphology of the CFP, macroreticular or gel-type, the metal nanoclusters in polymer-supported heterogeneous metal catalysts are... 

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