Copper oxide in layered tin oxide with intracrystalline microporosity for oxidative imination of toluene and p-xylene

Abstract

Homoepitaxial layered structure of tin oxide, SnO2 containing low amount of copper oxide, CuO (named as CuOSnO2) was found to convert toluene and p-xylene into value-added compounds. The CuO-SnO2 with microporous channels and expanded lattice planes allowed the high diffusion of toluene and p-xylene. Such characteristics features made the oxidative coupling of toluene and p-xylene with various amines resulting in different imines with good yield (70-92%) within 12 h. The reaction proceeded with the selective transformation from toluene to benzaldehyde and its condensation with amines at 120degree celsius in presence of H2O2 as oxidant. Theoretical investigations were done to understand to know the thermodynamic feasibility of the reaction. The same study also suggested the involvement of weak supramolecular forces like cation (Sn4+)-pi interactions in stabilizing the intermediate state during the course of the reaction. The thermally stable CuO-SnO2 catalysts with moderate to strong basic sites appeared as a suitable recyclable catalyst for the oxidative imination raction.