On the mechanism of model diesel soot-O2 reaction catalysed by Pt-containing La3+-doped CeO2: A TAP study with isotopic O2

Pt supported on CeO2 and 10 wt.% La3+-doped CeO2 catalysts have been prepared, characterised and tested for soot oxidation by O2 in TGA. The reaction mechanism has been studied in a TAP reactor with labelled O2. Isotopic oxygen exchange between molecular O2 and ‘O’ on the support/catalyst was observed and soot oxidation is being carried out by lattice oxygen. TAP studies further show that Pt improves O2 adsorption and, therefore, 5 wt.% Pt-containing catalysts are more active for soot oxidation than the counterpart supports. In addition, CeO2 doping by La3+ leads to an improved support, since La3+ stabilises the structure of CeO2 when calcined at high temperature (1000 °C) and minimises sintering. In addition, La3+ improves the Ce4+/Ce3+ reduction as deduced from H2-TPR experiments and favours oxygen mobility into the lattice. A synergetic effect of Pt and La3+ is observed, Pt-containing La3+-doped CeO2 being the most active catalyst for soot oxidation by O2 among the samples studied.