Selective liquid-phase oxidation of toluene to benzaldehyde and benzyl alcohol over CeO ₂ -MnO ₂ /NC: Solvent-/additive-free conditions with molecular oxygen

The selective oxidation of the side-chain C-H bonds in toluene to produce oxygen-containing aromatic compounds is a crucial transformation in organic synthesis. Herein, the solvent- and additive-free liquid-phase catalytic oxidation of toluene using molecular oxygen as the oxidant was carried out. This process enabled the highly selective synthesis of benzaldehyde (PhCHO) and benzyl alcohol (PhCH
2
OH) over a low-cost CeO
2
-MnO
2
/NC. The catalyst was fabricated via a one-pot pyrolysis method and characterized by a series of techniques, including nitrogen adsorption-desorption test, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H
2
-TPR), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy-elemental mapping (SEM-mapping), transmission electron microscopy (TEM) and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS). Characterization results indicate that the enhanced catalytic activity benefits from the synergistic effect between components and the good dispersion of amorphous Ce-Mn species. Under reaction conditions, the heterogeneous catalyst exhibited favorable selectivity, achieving 62.3% selectivity for PhCHO and PhCH
2
OH at a toluene conversion of 6.5%. This method utilizing CeO
2
-MnO
2
/NC as an efficient and low-cost catalyst, offers a novel and economical approach for the selective aerobic oxidation of toluene to PhCH
2
OH and PhCHO.