Three-way Catalysis with Noble Metal-Substituted La(Fe,Co)O3 Perovskites—the Role of Noble and Base Metal Components
2019
La(FexCo1-x)O3 perovskites with noble metals incorporated (Pd in different amounts, Pt, Rh; with Pd
at x = 1, 0.7, 0) were
prepared via the dry citrate method and examined with respect to their behavior in three-way
catalysis (lean and stoichiometric
model feeds containing CO, propene, NO, and O2) in the as-prepared state and after redox stress of
different severity (at
temperatures up 1173 K). Results were compared with data obtained with a commercial Pd-based
three-way catalyst.
Perovskites outperformed the reference in CO oxidation but were less active in propene oxidation
and NO reduction. While
their oxidation activity was rather stable, their NO reduction activity suffered severely from the
redox treatments unlike that of the
reference. It was concluded that oxidation and reduction reactions are catalyzed by different
sites. While the presence and the
nature of the noble metal were mostly irrelevant for oxidation reactions, in particular for CO
oxidation, NO reduction was
dominated by the contribution of the noble metal component. The inferior NO reduction activity
despite noble metal contents
of up to 2.5 wt% and the dominance of the perovskite surface in propene oxidation (compared with
high oxidation activity of Pd
in the reference catalyst) suggest that the metal component was not well exposed in the perovskite
catalysts.
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