Toluene abatement on Ag-CeO₂/SBA-15 catalysts: synergistic effect of silver and ceria

As a typical volatile organic compound, toluene is a hazardous material for human health and the environment, and currently, the development of catalysts for its oxidation into CO₂ and water is crucial. The series of Ag-CeO₂/SBA-15 catalysts is synthesized by wetness impregnation techniques and characterized by a number of physical-chemical methods (nitrogen [N₂] physisorption, small angle X-ray scattering [SAXS], transmission electron microscopy [TEM], and temperature-programmed reduction [TPR]). The toluene sorption and catalytic properties in toluene oxidation are studied. Small silver [Ag] and cerium oxide [ceria, CeO_2] particles with sizes below 3 nm are predominantly formed in the ordered structure of Santa Barbara Amorphous-15 [SBA-15]. The interactions between the Ag and CeO₂ nanoparticles are established. Temperature-programmed desorption of toluene [TPD-C₇H₈] analysis shows that physical adsorption of toluene occurs on pristine SBA-15 material, while the introduction of either silver or ceria to SBA-15 leads to the appearance of additional strongly bound chemisorbed toluene on such sites. When both Ag and CeO₂ are introduced, only chemisorbed toluene is formed over the Ag-CeO₂/SBA-15 catalyst, and the highest catalytic activity in toluene oxidation is observed over this catalyst (T_98% = 233 °C, 0.2% C₆H₅CH₃) that is attributed to the synergistic effect of ceria [CeO_2] and silver [Ag].