Structural and Compositional Effect of Heteropolyoxoanions [NiMo6-x WxO24H6]4- on the Catalytic Activity of Clean Selective Oxidation of Diphenylsulfide
Maria G. Egusquiza,
Irma L. Botto,
Carmen I. Cabello.
Diphenyilsulfide oxidation by H2O2 as oxidant was studied through the structural effect of the isomorphous
W-Mo systems, Anderson type, with [Ni(II)Mo(VI)6-xW(VI)xO24H6]4- composition. These phases were proved as alternative
catalysts instead of W and Mo conventional systems. The characterization of the substituted phases was carried out by
different physico-chemical techniques (AAS, DRS, micro-Raman, XRD, TPR). The catalytic evaluation for the phase
NiW6 revealed that the process was selective to the sulfone formation (selectivity ~ 81-88 %) while the Ni-Mo bi-metallic
system (NiMo6) was only selective to the sulfoxide production (selectivity 98 %). The activity was 90 % at 60 and 180
min for the NiMo6 and NiW6 respectively, whereas the substituted phases presented intermediate values. The observed
differences can be related to the strength of the bridge bonds (Mo-O…Ni and W-O…Ni) associated to the higher electronegativity
and ionic potential of Mo with respect to W. Hence, the W-O bond is more reactive by the inductive effect of
Ni, which produces a higher oxidation of diphenyilsulfide to give sulfone, considering the electronic mobility in the redox
Keywords: Clean oxidation, Diphenylsulfone, Diphenylsulfoxide, Hydrogen peroxide, Selective oxidation, W and Mo heteropolymetalates.
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