- Carbon-supported metal-modified lacunary tungstosilicic polyoxometallates used as catalysts in the selective oxidation of sulfides
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Lacunary tungstosilicic polyoxometallates modified with transition metal ions [SiW11O39M(H2O)]6-, where M = Mn2+, Fe2+, Co2+or Cu2+, were synthesized and supported on activated carbon to obtain the SiW11MC catalysts. The samples were characterized by FT-IR, XRD, N2 adsorption-desorption measurements, and the acidic properties were determined using the isopropanol dehydration test reaction. The activity and selectivity of the catalysts were evaluated in the selective oxidation of a series of sulfides to sulfoxides or sulfone. The reaction was carried out in acetonitrile as solvent using H2O2 35% p/V as a clean oxidant. The conversion values decreased in the following order: SiW11MnC > SiW11FeC > SiW11CuC > SiW11CoC. The catalysts were reused without appreciable loss of their catalytic activity. It was found that the activity of the catalysts decreases in parallel with the increment in the reduction temperature values. The most easily reducible catalyst displayed the highest conversion values. We found a convenient and selective procedure for oxidizing sulfides to sulfoxides or sulfones using aqueous hydrogen peroxide and a catalytic amount of lacunary tungstosilicic polyoxometallates supported on carbon at low temperatures (20-50 °C) in a reasonably short reaction time
- Frenzel, Romina,Sathicq, ángel G.,Blanco, Mirta N.,Romanelli, Gustavo P.,Pizzio, Luis R.
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- Selective Oxidation of Sulfides to Sulfoxides Using Modified Keggin Heteropolyacids as Catalyst
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The use of modified Keggin phosphomolybdic heteropolyacids (HPA) (V and Al) as catalysts in the selective oxidation of sulfides to the corresponding sulfoxides is reported. Excellent yields were obtained (13 examples: 79%-95%), using 35% (w/v) aqueous hydrogen peroxide as oxidant, and acetonitrile as solvent at 25°C. The relationship between the electron densities of the sulfur atoms, which was estimated by molecular theoretical calculations, and the oxidative relativities of the sulfur-containing compounds was also investigated. The results indicate that the time for 100% conversion decreases with an increase in electron density.
- Palermo, Valeria,Sathicq, Angel G.,Vazquez, Patricia G.,Romanelli, Gustavo P.
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- Heterocyclic amine salts of Keggin heteropolyacids used as catalyst for the selective oxidation of sulfides to sulfoxides
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A range of sulfides can be selectively oxidized to the corresponding sulfoxides in good yields using catalytic quantities of heterocyclic amine salts (quinoline, cinchonine, and cinchonidine) of Keggin heteropolyacids with different green oxidants. The cinchonine heteropolyacid catalyst is easily recoverable and reusable without loss of its catalytic activity, and an enantiomeric excess can be obtained.
- Sathicq, Angel G.,Romanelli, Gustavo P.,Palermo, Valeria,Vázquez, Patricia G.,Thomas, Horacio J.
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p. 1441 - 1444
(2008/09/18)
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