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Novel, benign, solid catalysts for the oxidation of hydrocarbons

Ratnasamy, P., Raja, R. and Srinivasi, D. (2005) Novel, benign, solid catalysts for the oxidation of hydrocarbons Philosophical Transactions of The Royal Society A, 363, (1829), pp. 1001-1012. (doi:10.1098/rsta.2004.1538).

Record type: Article

Abstract

The catalytic properties of two classes of solid catalysts for the oxidation of hydrocarbons in the liquid phase are discussed: (i) microporous solids, encapsulating transition metal complexes in their cavities and (ii) titanosilicate molecular sieves. Copper acetate dimers encapsulated in molecular sieves Y, MCM-22 and VPI-5 use dioxygen to regioselectively ortho-hydroxylate L-tyrosine to L-dopa, phenol to catechol and cresols to the corresponding o-dihydroxy and o-quinone compounds. Monomeric copper phthalocyanine and salen complexes entrapped in zeolite-Y oxidize methane to methanol, toluene to cresols, naphthalene to naphthols, xylene to xylenols and phenol to diphenols. Trimeric ?3-oxo-bridged Co/Mn cluster complexes, encapsulated inside Y-zeolite, oxidize para-xylene, almost quantitatively, to terephthalic acid. In almost all cases, the intrinsic catalytic activity (turnover frequency) of the metal complex is enhanced very significantly, upon encapsulation in the porous solids. Spectroscopic and electrochemical studies suggest that the geometric distortions of the complex on encapsulation change the electron density at the metal ion site and its redox behaviour, thereby influencing its catalytic activity and selectivity in oxidation reactions.
Titanosilicate molecular sieves can oxidize hydrocarbons using dioxygen when loaded with transition metals like Pd, Au or Ag. The structure of surface Ti ions and the type of oxo-Ti species generated on contact with oxidants depend on several factors including the method of zeolite synthesis, zeolite structure, solvent, temperature and oxidant. Although, similar oxo-Ti species are present on all the titanosilicates, their relative concentrations vary among different structures and determine the product selectivity.

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More information

Published date: 2005
Keywords: complexes, encapsulated metal, epoxidation reactions, phthalocyanine, cluster complexes, epr, ts-1, zeolite-y, titanosilicate molecular-sieves, solid catalysts, copper, benign catalytic oxidations, titanosilicate molecular sieves, active-sites, selective-oxidation

Identifiers

Local EPrints ID: 54199
URI: http://eprints.soton.ac.uk/id/eprint/54199
ISSN: 1364-503X
PURE UUID: 1605c6ea-c374-4661-9840-f2ce0a59f357

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Date deposited: 01 Aug 2008
Last modified: 15 Sep 2017 16:31

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Contributors

Author: P. Ratnasamy
Author: R. Raja
Author: D. Srinivasi

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