Improving ceria-zirconia soot combustion catalysts by neodymium doping

Authors: Ana M. Hernández-Giménez, Leandro P. dos Santos Xavier, Agustín Bueno-López

Abstract:
The effect of Nd doping on the physicochemical and catalytic properties for soot combustion of CeO₂ and CeO₂-ZrO₂ oxides has been studied. Four oxides with composition CeO₂, Ce_0.9Nd_0.1O₂, Ce_0.73Zr_0.27O₂ and Ce_0.64Zr_0.27Nd_0.09O₂ have been prepared by co-precipitation and calcination at 800^◦C, characterized by XRD, Raman Spectroscopy, N₂ adsorption and temperature programmed reduction by H₂, and tested for soot combustion with NOx/O₂. The catalytic activity for soot combustion of CeO₂ and Ce_0.9Nd_0.1O₂ was null due to thermal sintering (1 and 5 m2/g, respectively), and Zr-doping is mandatory to prevent such sintering. The best catalytic activity for soot combustion was obtained with Ce_0.64Zr_0.27Nd_0.09O₂ (37 m2/g), and as far as we know, it is the first time that this improvement on Ce-Zr soot combustion capacity by Nd doping is reported. Ce_0.64Zr_0.27Nd_0.09O₂ combines the beneficial effect of both Zr doping (improved thermal stability and redox properties) and Nd doping (additional benefit on redox properties by oxygen vacancies creation due to 3+ cations doping into the lattice). The highest activity for soot combustion of Ce_0.64Zr_0.27Nd_0.09O₂ is related with its highest NO oxidation capacity. As deduced by in situ DRIFTS experiments, Nd-doping into the Ce-Zr oxide favors the formation of less stable surface nitrogen species (nitrates and nitrites were detected) in comparison to those formed on Ce_0.73Zr_0.27O₂ (only nitrates were detected) providing alternative and faster NO₂ production pathways.

Keywords:
Diesel soot
Soot combustion
Ceria-zirconia catalyst
Neodymium-ceria catalyst
Nitrogen oxides

Published in: Applied catalysis A: General  (Volumes 462–463, Pages 1-310, 10 July 2013)

Publisher: Elsevier      

ISSN Information: 0926-860X

Improving ceria-zirconia soot combustion catalysts by neodymium doping

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