Kinetics and mechanism of o-aminophenol oxidation by the supported mesoporous silica (HISiO2) in the binary system with Amberlite resin

H1SiO2 (hexagonal mesoporous silica) was synthesized with a high concentration of a non-ionic template. The synthesized H1SiO2 materials have a well defined porous architecture with surface area (760 m(2) g(-1)), and pore size = 35 Angstrom. Cu(II)-aquo complex was anchored onto silica (S-Cu-II) through the coordination with amino-functionalized H1SiO2 (S-NH2) without impregnation on the surface, The oxidation of omicron-aminophenol (omicron-AP) with (S-Cu-II), Cu(II)-oxalate complex supported on Amberlite resin (R-Cu-II), (R-Cu-II)/S-NH2 (0.05 g), and a mixture (1:1) of (R-Cu-II)/(S-Cu-II), has been studied at different temperatures (25-40 degreesC) +/- 0.1. The oxidation product has been monitored kinetically and spectrophotometrically. All redox reactions were characterized by first-order kinetics. The rate constant of the oxidation reaction of omicron-AP decreases in the following order; (S-Cu-II) > (R-Cu-II)/(S-Cu-II) > (R-Cu-II)/(S-NH2) > (R-Cu-II). This sequence reflects the role of the effective surface area of H1SiO2 on the redox reaction. The activation parameters for the amine oxidation have been estimated. Besides, a mechanism of the oxidation process of omicron-AP has been proposed. (C) 2002 Elsevier Science B.V. All rights reserved.