DRIFTS studies on CO and NO adsorption and NO plus CO reaction over Pd2+-substituted CeO2 and Ce0.75Sn0.25O2 catalysts

Baidya, Tinku and Bera, Parthasarathi and Mukri, Bhaskar Devu and Panda, Sanjit Kumar and Kroecher, Oliver and Elsener, Martin and Hegde, MS (2013) DRIFTS studies on CO and NO adsorption and NO plus CO reaction over Pd2+-substituted CeO2 and Ce0.75Sn0.25O2 catalysts. In: Journal of Catalysis, 303 . pp. 117-129.

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Abstract

Sequential adsorption of CO and NO as well as equimolar NO + CO reaction with variation of temperature over Pd2+ ion-substituted CeO2 and Ce0.75Sn0.25O2 supports has been studied by DRIFTS technique. The results are compared with 2 at.% Pd/Al2O3 containing Pd-0. Both linear and bridging Pd-0-CO bands are observed over 2 at.% Pd/Al2O3. But, band positions are shifted to higher frequencies in Ce0.98Pd0.02O2-delta and Ce0.73Sn0.25Pd0.02O2-delta catalysts that could be associated with Pd delta+-CO species. In contrast, a Pd2+-CO band at 2160 cm(-1) is observed upon CO adsorption over Ce0.98Pd0.02O2-delta and Ce0.73Sn0.25Pd0.02O2-delta catalysts pre-adsorbed with NO and a Pd+-CO band at 2120 cm(-1) is slowly developed on Ce(0.73)Srl(0.25)Pd(0.02)O(2-delta) over time. An intense linear Pd-0-NO band at 1750 cm(-1) found upon NO exposure to CO pre-adsorbed 2 at.% Pd/Al2O3 indicates molecular adsorption of NO. On the other hand, a weak Pd2+-NO band at 1850 cm(-1) is noticed after NO exposure to Ce0.98Pd0.02O2-delta catalyst pre-adsorbed with CO indicating dissociative adsorption of NO which is crucial for NO reduction. Pd-0-NO band is initially formed over CO pre-adsorbed Ce0.73Sn0.25Pd0.02O2-delta which is red-shifted over time along with formation of Pd2+-NO band. Several intense bands related to nitrates and nitrites are observed after exposure of NO to fresh as well as CO pre-adsorbed Ce0.98Pd0.02O2-delta and Ce0.73Sn0.25Pd0.02O2-delta catalysts. Ramping the temperature in a DRIFTS cell upon NO and CO adsorption shows the formation of N2O and NCO surface species, and N2O-formation temperature is comparable with the reaction done in a reactor.

Item Type:	Journal Article
Publication:	Journal of Catalysis
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Keywords:	Adsorption; CO; NO; Reaction; DRIFTS; Ce0.98Pd0.02O2-Delta; Ce0.73Sn0.25Pd0.02O2-Delta
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	03 Sep 2013 07:00
Last Modified:	03 Sep 2013 07:00
URI:	http://eprints.iisc.ac.in/id/eprint/46966

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