Carbon-supported metal-modified lacunary tungstosilicic polyoxometallates used as catalysts in the selective oxidation of sulfides

R. FRENZEL; A. SATHICQ; M. BLANCO; G. ROMANELLI; D. BENNARDI, G. ROMANELLI, J. AUTINO, L. PIZZIO

JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015

1381-1169

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 aseries of sulfides to sulfoxides or sulfone. The reaction was carried out in acetonitrile as solventusing 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 incrementin the reduction temperature values. The most easily reducible catalyst displayed the highest conversionvalues. We found a convenient and selective procedure for oxidizing sulfides to sulfoxides or sulfonesusing aqueous hydrogen peroxide and a catalytic amount of lacunary tungstosilicic polyoxometallatessupported on carbon at low temperatures (20?50 °C) in a reasonably short reaction time