The role of WO x and dopants (ZrO 2 and SiO 2 ) on CeO 2 -based nanostructure catalysts in the selective oxidation of benzyl alcohol to benzaldehyde under ambient conditions.

Herein, the efficacy of WO x -promoted CeO 2 -SiO 2 and CeO 2 -ZrO 2 mixed oxide catalysts in the solvent-free selective oxidation of benzyl alcohol to benzaldehyde using molecular oxygen as an oxidant is reported. We evaluated the effects of the oxidant and catalyst concentration, reaction duration, and temperature on the reaction with an aim to optimize the reaction conditions. The as-prepared CeO 2 , CeO 2 -ZrO 2 , CeO 2 -SiO 2 , WO x /CeO 2 , WO x /CeO 2 -ZrO 2 , and WO x /CeO 2 -SiO 2 catalysts were characterized by X-ray diffraction (XRD), N 2 adsorption-desorption, Raman spectroscopy, temperature-programmed desorption of ammonia (TPD-NH 3 ), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). These characterisation results indicated that the WO x /CeO 2 -SiO 2 catalyst possessed improved physicochemical ( i.e. , structural, textural, and acidic) properties owing to the strong interactivity between WO x and CeO 2 -SiO 2 . A higher number of Ce 3+ ions ( I u''' / I Total ) were created with the WO x /CeO 2 -SiO 2 catalyst than those with the other catalysts in this work, indicating the generation of a high number of oxygen vacancies. The WO x /CeO 2 -SiO 2 catalyst exhibited a high conversion of benzyl alcohol (>99%) and a high selectivity (100%) toward benzaldehyde compared to the other promoted catalysts ( i.e. , WO x /CeO 2 and WO x /CeO 2 -ZrO 2 ), which is attributed to the smaller particle size of the WO x and CeO 2 and their high specific surface area, more significant number of acidic sites, and superior number of oxygen vacancies. The WO x /CeO 2 -SiO 2 catalyst could be quickly recovered and utilized at least five times without suffering any appreciable activity loss.