Monoterpenes oxidation in the presence of Y zeolite-entrapped manganese(III) tetra(4-N-benzylpyridyl)porphyrin

Abstract

Under homogeneous conditions and as a Y zeolite supported complex, manganese(III) tetra(4-N-benzylpyridyl)porphyrin (MnTBzPyP) is an active catalyst in the epoxidation of (R)-(+)-limonene and α-pinene, and in the hydroxylation of carvacrol and thymol, using H2O2/ammonium acetate, at room temperature and atmospheric pressure. A combined study on the characterization and catalytic performance of MnTBzPyP–NaY suggests that its preparation led to a successful inclusion of MnTBzPyP inside the zeolite during the hydrothermal synthesis. Unfortunately, irreversible catalyst deactivation occurs in the presence of H2O2. Changes in the crystalline structure of MnTBzPyP–NaY during the oxidative transformations are accompanied by leaching of the porphyrin complex to the reaction solution, accounting for the nearly complete loss of activity when the catalyst is re-used. Higher substrate conversions were achieved with the zeolite-impregnated complex. The iron analogue is inactive, under the applied reaction conditions.