Effect of Mn substitution on the promoted formaldehyde oxidation over spinel ferrite: Catalyst characterization, performance and reaction mechanism

The work reports the synthesis and characterization of manganese substituted spinel ferrites, and their application as catalysts for formaldehyde oxidation. Structure and cationic coordination environment of the prepared catalysts were investigated by XRD, Raman, XPS spectroscopy and TG-DSC analysis. Temperature-programmed reduction (TPR) was used to measure the reducibility of catalysts. The characterization results reveal the formation of spinel structure in all the synthetic catalysts. The Mn cations enrich on the surface in the valence of +3 and +4. Mn substitution obviously increases the lattice oxygen content, facilitates the reduction of ferrite, and enhances the oxidative ability of Fe3+ and Mn cations on the catalyst surface. The presence of Mn cations in spinel ferrite greatly improves its catalytic activity in formaldehyde oxidation, evidenced by the obvious decrease of 90% formaldehyde conversion temperature. The studied catalyst also displays high stability and superior activity in the presence of water vapor, which presents an applied interest. The remarkable effect of Mn substitution on the promoted formaldehyde oxidation over spinel ferrite catalysts was discussed in view of reaction mechanism and variations in microstructural environment and physicochemical properties of spine! ferrite. (C) 2015 Elsevier B.V. All rights reserved.