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

HISiO2 (hexagonal mesoporous silica) was synthesized with a high concentration of a non-ionic template. The synthesized HISiO2 materials have a well defined porous architecture with surface area (760 m2 g−1), and pore size=35 Å. Cu(II)–aquo complex was anchored onto silica (S–CuII) through the coordination with amino-functionalized HISiO2 (S–NH2) without impregnation on the surface. The oxidation of o-aminophenol (o-AP) with (S–CuII), Cu(II)-oxalate complex supported on Amberlite resin (R–CuII), (R–CuII)/S–NH2 (0.05 g), and a mixture (1:1) of (R–CuII)/(S–CuII), has been studied at different temperatures (25–40 °C) ±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 o-AP decreases in the following order; (S–CuII)>(R–CuII)/(S–CuII)>(R–CuII)/(S–NH2)>(R–CuII). This sequence reflects the role of the effective surface area of HISiO2 on the redox reaction. The activation parameters for the amine oxidation have been estimated. Besides, a mechanism of the oxidation process of o-AP has been proposed.