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Synthesis, phase stability and catalytic activity of Pd-doped La-based perovskites during SCR-NO<sub>x</sub> with C<sub>3</sub>H<sub>6</sub>

Mondragon Rodriguez, G.C. and Saruhan, B. (2008) Synthesis, phase stability and catalytic activity of Pd-doped La-based perovskites during SCR-NO<sub>x</sub> with C<sub>3</sub>H<sub>6</sub>. In: 2008 5th International Conference on Environmental Catalysis. 2008 (5th International Conference on Environmental Catalysis, 2008-08-31 - 2008-09-04, Belfast, UK.

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A wide variety of gperovskite combinations functions as host materials for precious metals (e.g. Pt, Rh, Pd, Ru). This is because the synergic interaction between the metal and the host perovskite structure occurs under redox conditions leading to improved catalytic properties [1]. As it is reported, a reversible diffusion of Pd ions in and out of the crystal lattice takes place under stochimetric combustion (λ = 1) conditions [2]. We studied the redox behaviour of LaFe<sub>0.65</sub>Co<sub>(0.35-x)</sub>Pd<sub>x</sub>O<sub>3</sub> (x=0, 0.05) catalysts under lean-burn conditions and tested its catalytic performance during the SCR NO<sub>x</sub>-reaction with C<sub>3</sub>H<sub>6</sub>. A modified citrate route was successfully employed to synthesize palladium substituted perovskites. XRD results show the presence of pure orthorhombic perovskite with composition LaFe<sub>0.65</sub>Co<sub>0.3</sub>Pd<sub>0.05</sub>O<sub>3</sub> that begins to crystallize at approx. 600°C and completes its crystallization at temperatures slightly below 700°C. According to the crystallization behaviour we can postulate that our catalyst is metastable up to 700°C. Our XPS results show that this catalyst displays a reversible behaviour under redox conditions. The exposure of the LaFe<sub>0.65</sub>Co<sub>0.3</sub>Pd<sub>0.05</sub>O<sub>3</sub> catalyst calcined preliminary at 700°C to 5 vol.% H<sub>2</sub> in N<sub>2</sub> at 600°C/1h leads to diffusion of Pd ions as metallic sites (10 to 15 nm size) which reversibly disappear after re-oxidation process in static air at 600°C/1h as detected with ex-situ SEM and TEM analysis. The catalytic test during the SCR-NO<sub>x</sub> with C<sub>3</sub>H<sub>6</sub> model reaction shows an improved catalytic performance of the Pd-doped perovskite (LaFe<sub>0.65</sub>Co<sub>0.3</sub>Pd<sub>0.05</sub>O<sub>3</sub>) catalyst compared to the Pd-supported (Pd/LaFe<sub>0.65</sub>Co<sub>0.35</sub>O<sub>3</sub>-700°C) catalyst. The Pd-free perovskite LaFe<sub>0.65</sub>Co<sub>0.35</sub>O<sub>3</sub>-700°C shows only a negligible activity under the same reaction conditions. The LaFe<sub>0.65</sub>Co<sub>0.3</sub>Pd<sub>0.05</sub>O<sub>3</sub>-700°C catalyst shows a NO conversion up to 40 % of at 275°C even at high space velocities (SV~220.800 hr<sup>-1</sup>). [1] H. Tanaka, M. Misono, Current Opinion in Sol. State and Mat Sci. 5 (2001) 381-387. [2] Y. Nishihata, J. Mizuki, T. Akao, H. Tanaka, M. Kimura, T. Okamoto and H. Hamada, Nature 418, 164-167 (2002).

Item URL in elib:https://elib.dlr.de/55207/
Document Type:Conference or Workshop Item (Poster)
Title:Synthesis, phase stability and catalytic activity of Pd-doped La-based perovskites during SCR-NO<sub>x</sub> with C<sub>3</sub>H<sub>6</sub>
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Date:September 2008
Journal or Publication Title:2008 5th International Conference on Environmental Catalysis
Refereed publication:No
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
Keywords:Pd-doped perovskite, NOx-reduction, lean-burn
Event Title:2008 (5th International Conference on Environmental Catalysis
Event Location:Belfast, UK
Event Type:international Conference
Event Dates:2008-08-31 - 2008-09-04
Organizer:Queen´s University Belfast
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Aeronautics
HGF - Program Themes:Propulsion Systems (old)
DLR - Research area:Aeronautics
DLR - Program:L ER - Engine Research
DLR - Research theme (Project):L - Low-Emission Air Traffic (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Research > High Temperature and Functional Coatings
Deposited By: Mondragon Rodriguez, Guillermo Cesar
Deposited On:09 Sep 2008
Last Modified:27 Apr 2009 15:12

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