Catalytic Oxidation of CO and Soot over Ce-Zr-Pr Mixed Oxides Synthesized in a Multi-Inlet Vortex Reactor: Effect of Structural Defects on the Catalytic Activity

Samir Bensaid; Marco Piumetti; Chiara Novara; Fabrizio Giorgis; Angelica Chiodoni; Nunzio Russo; Debora Fino

doi:10.1186/s11671-016-1713-1

Catalytic Oxidation of CO and Soot over Ce-Zr-Pr Mixed Oxides Synthesized in a Multi-Inlet Vortex Reactor: Effect of Structural Defects on the Catalytic Activity

Nanoscale Res Lett. 2016 Dec;11(1):494. doi: 10.1186/s11671-016-1713-1. Epub 2016 Nov 10.

Authors

Samir Bensaid¹, Marco Piumetti², Chiara Novara¹, Fabrizio Giorgis¹, Angelica Chiodoni³, Nunzio Russo¹, Debora Fino¹

Affiliations

¹ Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino, Italy.
² Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino, Italy. marco.piumetti@polito.it.
³ Center for Sustainable Futures - CSF@POLITO, Istituto Italiano di Tecnologia, Corso Trento 21, Torino, 10129, Italy.

Abstract

In the present work, ceria, ceria-zirconia (Ce = 80 at.%, Zr = 20 at.%), ceria praseodymia (Ce = 80 at.%, Pr = 20 at.%) and ceria-zirconia-praseodymia catalysts (Ce = 80 at.%, Zr = 10 at.% and Pr = 10 at.%) have been prepared by the multi-inlet vortex reactor (MIVR). For each set of samples, two inlet flow rates have been used during the synthesis (namely, 2 ml min^-1_, and 20 ml min^-1) in order to obtain different particle sizes. Catalytic activity of the prepared materials has been investigated for CO and soot oxidation reactions. As a result, when the catalysts exhibit similar crystallite sizes (in the 7.7-8.8 nm range), it is possible to observe a direct correlation between the O_v/F_2g vibrational band intensity ratios and the catalytic performance for the CO oxidation. This means that structural (superficial) defects play a key role for this process. The incorporation of Zr and Pr species into the ceria lattice increases the population of structural defects, as measured by Raman spectroscopy, according to the order: CeO₂ < Ce₈₀Zr₂₀ < Ce₈₀Zr₁₀Pr₁₀ < Ce₈₀Pr₂₀. On the other hand, the presence of zirconium and praseodymium into the ceria lattice does not have a direct beneficial effect on the soot oxidation activity for these catalysts, in contrast with nanostructured ones (e.g., Ce-Zr-O nanopolyhedra, Ce-Pr-O nanocubes) described elsewhere (Andana et al. Appl. Catal. B 197: 125-137, 2016; Piumetti et al., Appl Catal B 180: 271-282, 2016).

Keywords: CO oxidation; Ceria; Dopants; Praseodymia; Soot oxidation; Structural defects; Zirconia.