Iron and copper immobilised on mesoporous MCM-41 molecular sieves as catalysts for the oxidation of cyclohexane

Abstract

A pure silica mesoporous molecular sieve analogous to MCM-41 (Si-MCM-41) was organofunctionalised with 3-aminopropyltrimethoxysilane. The resulting organofunctionalised Si-MCM-41 ((NC 3)Si-MCM-41) was suspended in alcoholic solutions of iron and copper salts to form the respective metal complexes (M(NC 3)Si-MCM-41). Iron and copper were also incorporated into the framework of mesoporous MCM-41 metallosilicates (M-MCM-41) by hydrothermal synthesis. All these catalysts were employed in the liquid phase oxidation of cyclohexane with aqueous H 2O 2 (30%). The results show that the M(NC 3)Si-MCM-41 are more active than the corresponding M-MCM-41. The activity of the catalysts decreases in the following order: Fe(NC 3)Si-MCM-41≫Fe-MCM-41≫Cu(NC 3)Si-MCM-41≫Cu-MCM-41. However, when the catalysts are recycled, leaching of the metals is observed. The good catalytic activity found for Fe(NC 3)Si-MCM-41 can be attributed to the heterogenised iron complex.