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Functional Pd-substituted perovskite as catalyst for NO<sub>x</sub>-reduction under lean conditions

Mondragon Rodriguez, G.C. and Saruhan, B. (2008) Functional Pd-substituted perovskite as catalyst for NO<sub>x</sub>-reduction under lean conditions. In: [2008 Verona Second International Conference on Ceramics]. 2008( 2nd International Congress on Ceramics), 2008-06-29 - 2008-07-04, Verona, Italy.

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Abstract

Global warming is probably enhanced by the emission of greenhouse gases such as H<sub>2</sub>O<sub>vapour</sub>, CO<sub>2</sub>, and NO<sub>x</sub> which are produced in every combustion process. Weight reduction is an indirect way to reduce the products of combustion of fossil fuels in automotive or aircraft engines and power turbines. Weight savings result in lower fuel consumption and decrease of toxic emissions. Nitrogen oxides (cumulative named NO<sub>x</sub>) are present in the rich exhaust of gasoline engines and are effectively reduced to N<sub>2</sub> and O<sub>2</sub> by employing a Three Way Catalyst (TWC). On the other hand combustion under lean-burn conditions (in the presence of excess oxygen) is a preferred application, since it leads to higher fuel efficiency as in the case of diesel or aircraft engines when compared to the stoichiometric gasoline engines. Under excess oxygen the TWCs cannot eliminate NO<sub>x</sub>. That is why new catalytic systems and concepts are needed to completely remove NO<sub>x</sub> and other emissions from diesel engines and eventually turbines. Moreover, as the current application areas order, NO<sub>x</sub> must be eliminated under the presence of high oxygen concentrations and at relatively wide temperature window (100°-600°C). In this work we propose a palladium substituted lanthanum-based perovskite (LaFe<sub>0.65</sub>Co<sub>0.35-x</sub>Pd<sub>x</sub>O<sub>3</sub>) as catalyst for effective NO<sub>x</sub>-reduction under lean conditions. The bi-functional perovskite was synthesized by means of a modified citrate route. The Pd-doped perovskite powder (LaFe<sub>0.65</sub>Co<sub>0.35-x</sub>Pd<sub>x</sub>O<sub>3</sub>) shows high activity during selective reduction of NO<sub>x</sub> using hydrogen as a reducing agent. A NO<sub>x</sub> conversion of maximum 70% was detected at app. 210°C using a model gas mixture having 720ppm NO, 5%O<sub>2</sub>, 1%H<sub>2 and He as balance at a space velocity of 55 200h<sup>-1</sup>. Slight decrease </sub>in NO<sub>x</sub>-conversion to approx. 60% was observed with the presence of H<sub>2</sub>O<sub>vapour</sub> + CO<sub>2</sub> in the feed. The presence of CO in the mixture caused a strong negative impact on the NOx-conversion capacity of the perovskite catalyst. 40% of NO<sub>x</sub> conversion was measured at 200°C for a model gas mixture including CO. The Pd-substituted perovskite (LaFe<sub>0.65</sub>Co<sub>0.35-x</sub>Pd<sub>x</sub>O<sub>3</sub>) was coated on top of cordierite substrates of 400cpsi (cells per square inch) using silica as a binder. A catalyst thickness of approx. 20 μm is achieved. The catalytic test of this system demonstrates its applicability at lean automotive exhausts. Approx. 20 % of NO<sub>x</sub>-reduction was observed for a catalytic test with a model gas mixture having 500ppmNO, 1vol. % O<sub>2</sub> and C<sub>3</sub>H<sub>6</sub> in the presence of 4 % H<sub>2</sub>O<sub>vapour</sub> at a space velocity of 60 000h<sup>-1</sup>. The catalytic converter yields and effective NO<sub>x</sub>-reduction capacity in the presence of water vapour.

Item URL in elib:https://elib.dlr.de/55200/
Document Type:Conference or Workshop Item (Poster)
Title:Functional Pd-substituted perovskite as catalyst for NO<sub>x</sub>-reduction under lean conditions
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Mondragon Rodriguez, G.C.UNSPECIFIEDUNSPECIFIED
Saruhan, B.UNSPECIFIEDUNSPECIFIED
Date:2008
Journal or Publication Title:[2008 Verona Second International Conference on Ceramics]
Refereed publication:No
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:Perovskite, lean-burn, NOx-reduction
Event Title:2008( 2nd International Congress on Ceramics)
Event Location:Verona, Italy
Event Type:international Conference
Event Dates:2008-06-29 - 2008-07-04
Organizer:European Ceramic Society
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):E - Schadstoffe (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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