An investigation of the NO/H-2/O-2 (lean de-NOx) reaction on a highly active and selective Pt/La0.7Sr0.2Ce0.1FeO3 catalyst at low temperatures (Journal article)

Costa, C. N./ Savva, P. G./ Andronikou, C./ Lambrou, P. S./ Polychronopoulou, K./ Belessi, V. C./ Stathopoulos, V. N./ Pomonis, P. J./ Efstathiou, A. M.

A 0.1 wt% Pt supported on La0.7Sr0.2Ce0.1FeO3 solid (mixed oxide containing LaFeO3, SrFeO3-x, CeO2, and Fe2O3 phases) has been studied for the NO/H-2/O-2 reaction in the 100-400degreesC range. For a critical comparison, 0.1 wt% Pt was supported on SiO2, CeO2, and Fe2O3 and tested under the same reaction conditions. For the Pt/La0.7Sr0.2Ce0.1FeO3 catalyst a maximum in the NO conversion (83%) has been observed at 150degreesC with a N-2 selectivity value of 93%, while for the Pt/SiO2 catalyst at 120degreesC (82% conversion) with a N-2 selectivity value of 65% using a GHSV of 80,000 h(-)1 Low N-2 selectivity values, less than 45%, were obtained with the Pt/CeO2 and Pt/Fe2O3 catalysts in the 100-400degreesC range. For the Pt/La0.7Sr0.2Ce0.1FeO3 catalyst, addition of 5% H2O in the feed stream at 140degreesC resulted in a widening of the operating temperature window with appreciable NO conversion and no negative effect on the stability of the catalyst during 20 h on stream. In addition, a remarkable N-2 yield (93%) after 20 h on 0.25% NO/1% H-2/5% O-2/5% H2O/He gas stream at 140degreesC has been observed. Remarkable N-2 selectivity values in the range of 80-90% have also been observed in the 100-200degreesC low-temperature range either in the absence or in the presence of water in the feed stream. A maximum specific integral reaction rate of 443.5 mumol N-2/S . 9 Of Pt metal was measured at 160degreesC during reaction with a 0.25% NO/1% H-2/5% O-2/5% H2O/He gas mixture. This value is higher by 90% than the corresponding one observed on the 0.1 wt% Pt/SiO2 catalyst at 120degreesC and it is the highest value ever reported for the reaction at hand in the 100-200degreesC low-temperature range on Pt-based catalysts. A TOF value of 13.4 x 10(-2) s(-1) for N-2 formation was calculated at 110degrees'C for the Pt/La0.7Sr0.2Ce0.1FeO3 catalyst. Temperature-programmed desorption (TPD) of NO and transient titration experiments of the catalyst surface following NO/H-2/O-2 reaction have revealed important information concerning the amount and chemical composition of active and inactive (spectator) adsorbed N-containing species present under reaction conditions. (C) 2002 Elsevier Science (USA).
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας
Keywords: lean de-nox,no reduction,no tpd,perovskites,noble-metal catalysts,nitric-oxide,nitrogen monoxide,carbon-monoxide,no+h-2 reaction,burn conditions,excess oxygen,plus co,reduction,h-2
ISSN: 0021-9517
Link: <Go to ISI>://000176916300018
Publisher: Elsevier
Appears in Collections:Άρθρα σε επιστημονικά περιοδικά ( Ανοικτά)

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