New sol-gel catalytic materials for liquid-phase oxidations (Abstract/Poster in convegno)

  • New sol-gel catalytic materials for liquid-phase oxidations (Abstract/Poster in convegno) (literal)
  • 1999-01-01T00:00:00+01:00 (literal)
Alternative label
  • Rosaria Ciriminna, David Avnir and Mario Pagliaro (1999)
    New sol-gel catalytic materials for liquid-phase oxidations
    in New frontiers for catalytic membrane reactors and other membrane systems, Ravello, Italy, 23-27 maggio 1999
  • Rosaria Ciriminna, David Avnir and Mario Pagliaro (literal)
  • Poster (literal)
  • Rosaria Ciriminna, Mario Pagliaro, Istituto di Chimica e Tecnologia dei prodotti Naturali (ICTPN ora U.O. dell'ISMN), Palermo, Italy. David Avnir, Institute of Chemistry, The Hebrew University of Jerusalem (Israel). (literal)
  • New sol-gel catalytic materials for liquid-phase oxidations (literal)
  • The conversion of organic alcohols into corresponding carbonyl derivatives represents a class of chemical transformations of huge importance, since alcohol oxidations are employed for the preparation of pharmaceuticals, food additives, ingredients in cosmetics and synthetic precursors. Obvious environmental and economic reasons make of primary importance the substitution of current stoichiometric oxidation processes employing heavy metals and mineral acids, with catalytic oxidations using clean, cheap oxidants such as air or hypochlorite. A major advancement was accomplished by the chemistry Institute ICTPN of Palermo that culminated in a joint PCT patent application with the 'father' of the sol-gel chemistry of doped materials, Professor David Avnir, at the Hebrew University of Jerusalem. Microporous silica samples were prepared by the sol-gel procedure (hydrolysis and polymerization of alkoxysilanes) doped with stable organic nitroxyl radicals. Such microporous materials are effective in promoting the liquid phase (both in water and organic solvent) selective oxidation of several alcoholic substrates with clean oxidants like air (with Cu+) and moderately alkaline hypobromite (pH 10). Inorganic membranes doped (physically and chemically) with chemical species belonging to the family of nitroxyl radical 2,2,6,6 tetramethyl-1-piperydinyloxy (TEMPO) are suitable candidates for the replacement of above mentioned stoichiometric oxidants since they can be employed in a wide class of alcoholic oxidations with several primary oxidants - oxidations including vitamin C (ascorbic acid) preparation starting from sorbose. The technology represents indeed the fusion of 2 higly effective and innovative technologies known for their striking versatility: sol-gel chemistry that allows the preparation of modified inorganic membranes like the ORMOSILS in a huge (and amenable to be tailored) range of structural properties, along with the catalytic oxidations mediated by nitroxyl radicals, that in turn are most selective end effective catalysts of homogeneous liquid-phase oxidations of alcohols, including delicate substrates such as carbohydrates, hormones, allylic alcohols. Work is being carried out towards the improvement of material effectiveness (rate and recyclability) focusing efforts on the preparation of mesoporous sol-gel membranes either in the form of areogels (sol-gel materials obtained by cryogenic drying), as well as membranes made of thin films of sol-gel doped silica supported volcanic pumice. While development of technology continues, contacts are in course with multinational fine chemistry industries for the release of the technology. (literal)
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