Development of Molybdenum oxide Promoted CeO₂-SiO₂ Mixed-oxide Catalyst for Efficient Catalytic Oxidation of Benzylamine to N-Benzylidenebenzylamine

This study explores a rational synthesis of a molybdenum-promoted Ce-Si mixed oxide catalyst (MoO3/CeO2-SiO2) to regulate synergies between MoO3 and SiO2 dopant on CeO2, achieving high selectivity in solvent-free catalytic oxidative coupling of amines to imines using molecular O-2 as the oxidant. Comparative efficiency tests were conducted with bare CeO2, CeO2-SiO2, and MoO3/CeO2 catalysts. Characterization techniques, including XRD, Raman spectroscopy, N-2-adsorption-desorption analysis, FTIR, NH3-TPD, TEM, and XPS, were employed to assess textural properties, acidic features, promoter and dopant dispersion in CeO2 lattice, and oxygen defects. Mo/Ce-Si catalyst exhibited superior acidic sites and a higher concentration of Ce3+ ions (I-u/I-Total), indicating increased oxygen vacancies. This catalyst demonstrated exceptional performance in the oxidative coupling of benzylamine, providing higher conversion and selectivity to the corresponding imine. Remarkably, the Mo/Ce-Si catalyst maintained consistent performance over five recycling runs. The catalyst also proved effective for the selective oxidative coupling of various amine substrates with diverse steric and electronic properties. Experimental results confirmed a plausible reaction mechanism within the concise catalyst design.