Kinetics and mechanism of o-aminophenol oxidation by the supported mesoporous silica (H_ISiO₂) in the binary system with Amberlite resin

H_ISiO₂ (hexagonal mesoporous silica) was synthesized with a high concentration of a non-ionic template. The synthesized H_ISiO₂ 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-Cu^II) through the coordination with amino-functionalized H_ISiO₂ (S-NH₂) without impregnation on the surface. The oxidation of o-aminophenol (o-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°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-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 H_ISiO₂ 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.