Contact dynamics for a solid-solid reaction mediated by gas-phase oxygen: Study on the soot oxidation over ceria-based catalysts

Ceria-based Catalysts with different topological and textural properties have been prepared to study the role of the soot-catalyst contact on the soot oxidation reaction. The physico-chemical features of the catalysts have been investigated by means of complementary techniques, such as powder XRD, N-2 physisorption at -196 degrees C, optical microscopy at variable temperature, FESEM, TEM, and thermogravimetric analysis. As a whole, the best catalytic activity has been obtained with the CeO2-hanocubes (denoted to as Ce-NC) because of their higher intrinsic reactivity. On the other hand, high-surface area materials prepared by the cerium nitrate decomposition (dehoted to as Ce-ND) or hydrothermal route (CeO2-stars,referred to as Ce-SAS) resulted less effective toward the soot combustion, confirming the surface-sensitivity for this reaction. Moreover, it has been proven a higher dependence of the oxidation activity on the catalyst-to-soot ratio (wt./wt.) for the nanostructured catalyst (Ce-NC) exhibiting the lowest BET specific surface area (S-BET =4 m(2) g(-1)). On the other hand, the accessible (real) surface area, at variance of the BET surface area, seems to play a relevant role for this solid-solid reaction mediated by gas-phase oxygen. (C) 2016 Elsevier B.V. All rights reserved.