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.
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 Ov/F2gvibrational 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).
Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino, Italy.
Samir
S
Bensaid
Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino, Italy. marco.piumetti@polito.it.
Marco
M
Piumetti
Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino, Italy.
Chiara
C
Novara
Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino, Italy.
Fabrizio
F
Giorgis
Center for Sustainable Futures - CSF@POLITO, Istituto Italiano di Tecnologia, Corso Trento 21, Torino, 10129, Italy.
Angelica
A
Chiodoni
Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino, Italy.
Nunzio
N
Russo
Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino, Italy.
Debora
D
Fino
CO oxidation; Ceria; Dopants; Praseodymia; Soot oxidation; Structural defects; Zirconia