Dramatically promoted toluene destruction over Mn@Na-Al2O3@Al monolithic catalysts by Ce incorporation: Oxygen vacancy construction and reaction mechanism

Abstract

• A series of Mn-Ce@Na-Al 2 O 3 @Al mesh monolithic catalysts were facilely prepared. • Appropriate Ce doping can obviously enhance the toluene oxidation efficiency. • Ce species promotes the adsorption of oxygen and toluene molecules. • Oxygen vacancies can form easier on Ce modified monolithic catalysts. • Benzoate species oxidation was the rate determining step in toluene destruction. Here, a series of Mn-Ce binary oxides loaded monolith catalysts, with the support consisting of Na-Al 2 O 3 grown on Al mesh obtained by steam vapor treating, were prepared to attain efficient toluene destruction. On increasing CeO 2 loading, the toluene conversion over prepared catalysts shows an exponential rise, with Mn-4Ce@Na-Al 2 O 3 @Al monolithic catalyst exhibiting the optimal performance, over which 90% of toluene can be decomposed at 239 °C with oxidation rate over 5.57 × 10 −7 mol·g −1 ·s −1 , obviously higher than those over 4Ce/Na-Al 2 O 3 @Al (239 °C; 0.99 × 10 −7 mol·g −1 ·s −1 ) and Mn/Na-Al 2 O 3 @Al (291 °C; 4.12 × 10 −7 mol·g −1 ·s −1 ). H 2 -TPR and XPS results reveal that the superior redox ability and the formation of MnCeO x solid solution are favorable for toluene abatement. Oxygen vacancies form easily on the surface of Ce modified samples, resulting in superior oxygen and toluene adsorption ability, as demonstrated by DFT theoretical calculation. Besides, the pathways of toluene oxidation over Mn-4Ce@Na-Al 2 O 3 @Al catalyst were identified by using the in situ DRIFTS, and the key intermediates of toluene oxidation reaction are determined to be benzoyl, benzaldehyde, and benzoate.