Understanding the synergistic catalytic effect between La2O3 and CaO for the CH4 lean De-NOx reaction: Kinetic and mechanistic studies
Φόρτωση...
Ημερομηνία
Συγγραφείς
Anastasiadou, T.
Loukatzikou, L. A.
Costa, C. N.
Efstathiou, A. M.
Τίτλος Εφημερίδας
Περιοδικό ISSN
Τίτλος τόμου
Εκδότης
American Chemical Society
Περίληψη
Τύπος
Είδος δημοσίευσης σε συνέδριο
Είδος περιοδικού
peer reviewed
Είδος εκπαιδευτικού υλικού
Όνομα συνεδρίου
Όνομα περιοδικού
Journal of Physical Chemistry B
Όνομα βιβλίου
Σειρά βιβλίου
Έκδοση βιβλίου
Συμπληρωματικός/δευτερεύων τίτλος
Περιγραφή
Doping of La2O3 crystallites with Ca2+ ions significantly enhances the intrinsic rate of NO reduction by CH4 in the presence of 5% O-2 at 550 degrees C compared to pure La2O3 and CaO solids, while the opposite is true after doping of CaO with La3+ ions. It was found that the 5 wt % La2O3-95 wt % CaO system has one of the highest intrinsic site reactivities (TOF = 8.5 x 10(-3) s(-1)) reported at 550 degrees C for the NO/CH4/O-2 reaction among metal oxide surfaces. The doping process occurred after first dispersing La2O3 and CaO crystallites in deionized water heated to 60 degrees C for 90 min, while the dried material was then ground and heated slowly in air to 800 degrees C and kept at this temperature for 5 h. The doping process had the effect of creating surface oxygen vacant sites (F-type defects) in the oxide lattices the concentration of which is a function of the wt % La2O3 used in the mixed oxide system as revealed by photoluminescence and O-2 chernisorption studies. According to DRIFTS (NO)-N-15 transient isotopic experiments (SSITKA), oxygen vacant sites in Ca2+-doped La2O3 promote the formation of a more active chemisorbed NOx species (NO2-) that contributes to the enhancement of reaction rate as compared to pure lanthana, calcium oxide, and La3+-doped CaO. These results were supported by the kinetic orders of the reaction with respect to NO and O-2 obtained as a function of wt % La2O3 content in the mixed oxide system. Carbon dioxide (a reaction product) competes for the same oxygen vacant sites to form stable adsorbed carbonate-like species, thus lowering the reduction rate of NO. The dependence of the reaction TOF on the wt % La2O3 loading at 550 degrees C was found to follow the trend of the dependence of photoluminescence intensity on the wt % La2O3 content in the La2O3-CaO oxide system.
Περιγραφή
Λέξεις-κλειδιά
silica-supported platinum, nitric-oxide, selective reduction, n2o decomposition, calcium-oxide, earth-oxides, plus co, methane, adsorption, surface
Θεματική κατηγορία
Παραπομπή
Σύνδεσμος
<Go to ISI>://000230526800042
http://pubs.acs.org/doi/pdfplus/10.1021/jp0515582
http://pubs.acs.org/doi/pdfplus/10.1021/jp0515582
Γλώσσα
en
Εκδίδον τμήμα/τομέας
Όνομα επιβλέποντος
Εξεταστική επιτροπή
Γενική Περιγραφή / Σχόλια
Ίδρυμα και Σχολή/Τμήμα του υποβάλλοντος
Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας