Heterogenization of (nBu4N)4W10O32 on amorphous and MCM-41 silicas by impregnation is a suitable method to prepare efficient and stable catalysts able to oxidize unactivated C-H bonds to the corresponding alcohols and ketones with molecular oxygen and near ultraviolet light. The thus-prepared catalysts were characterized by spectroscopic and N2 adsorption-desorption experiments. A better dispersion of decatungstate was achieved with MCM-41, which also has a higher surface area. Results obtained in the model photooxidation of cyclohexane and cyclododecane confirm that the decatungstate heterogenized on the more ordered MCM-41 silica promotes the process with higher chemoselectivity (cyclohexanone/cyclohexanol molar ratio =2.6). The photocatalytic efficiency of (nBu4N)4W10O32 is not reduced after heterogenization; moreover, decatungstate immobilized on amorphous silica oxidizes cyclododecane with a markedly higher efficiency than in homogeneous phase. the supported photocatalysts can be used at least three times without any loss of activity.
IMMOBILIZATION OF (nBu4N)4W10O32 ON MESOPOROUS MCM-41 AND AMORPHOUS SILICAS FOR PHOTOCATALYTIC OXIDATION OF CYCLOALKANES WITH MOLECULAR OXYGEN
MALDOTTI, Andrea;MOLINARI, Alessandra;VARANI, Graziano;
2002
Abstract
Heterogenization of (nBu4N)4W10O32 on amorphous and MCM-41 silicas by impregnation is a suitable method to prepare efficient and stable catalysts able to oxidize unactivated C-H bonds to the corresponding alcohols and ketones with molecular oxygen and near ultraviolet light. The thus-prepared catalysts were characterized by spectroscopic and N2 adsorption-desorption experiments. A better dispersion of decatungstate was achieved with MCM-41, which also has a higher surface area. Results obtained in the model photooxidation of cyclohexane and cyclododecane confirm that the decatungstate heterogenized on the more ordered MCM-41 silica promotes the process with higher chemoselectivity (cyclohexanone/cyclohexanol molar ratio =2.6). The photocatalytic efficiency of (nBu4N)4W10O32 is not reduced after heterogenization; moreover, decatungstate immobilized on amorphous silica oxidizes cyclododecane with a markedly higher efficiency than in homogeneous phase. the supported photocatalysts can be used at least three times without any loss of activity.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
