“…NO coverage on all these oxides were found to be of the same order of magnitude as those measured for the simple oxides . The infrared spectra of NO adsorbed on the manganite LaMnO 3 showed bands of dinitrosyls and nitrite and nitrate species . This finding indicates that NO molecule interacts either through Mn 3+ ions (dinitrosyls) or through O 2- ions (nitrite and nitrates) as illustrated in the scheme: …”
Section: Co and No Adsorptionmentioning
confidence: 53%
“…48 The infrared spectra of NO adsorbed on the manganite LaMnO 3 showed bands of dinitrosyls and nitrite and nitrate species. 47 This finding indicates that NO molecule interacts either through Mn 3+ ions (dinitrosyls) or through O 2ions (nitrite and nitrates) as illustrated in the scheme: Successive NO-CO and CO-NO adsorptions on LaMO 3 at 298 K showed an inhibiting effect of NO on subsequent CO adsorption, and this was larger than the inhibiting effect of CO on NO adsorption. 39 NO adsorbs more strongly than CO, in accordance with previous observations by Yao and Shelef 48 for other perovskites.…”
Section: Co and No Adsorptionmentioning
confidence: 94%
“…This observation suggests that the nature of the adsorption is not altered with temperature. For LaCrO 3 , LaMnO 3 , and LaRhO 3 , the temperature interval where NO adsorption changes moderately (below 20%) was narrower. NO coverage on all these oxides were found to be of the same order of magnitude as those measured for the simple oxides .…”
Section: Co and No Adsorptionmentioning
confidence: 94%
“…Consistent with this, comparison of the thermodynamic parameters for the adsorption of NO and CO on LaCrO 3 revealed higher adsorption enthalpy and lower adsorption entropy for NO than for CO. The almost constancy of the amounts of adsorbed NO with temperature as well as the strength of the NO-surface bond are arguments in favor of the use of NO instead CO for determining metallic sites. ,,,, However, the complex IR spectra of chemisorbed NO 39,42,45 indicate that there is no specificity for the adsorption on metal or cation sites, and, therefore, the assumption of a 1:1 stoichiometry between NO and B 3+ sites may not give a proper estimate of the density of surface transition-metal sites. Thus, the CO molecule, whose interaction with B 3+ ions is weaker than with NO at temperatures close to ambient, is recommended for evaluating B 3+ cations in perovskite oxides.…”
He obtained his Ph.D. in chemistry in 1990 at the same university, working under the supervision of Dr. L. Gonza ´lez Tejuca and Prof. J. L. G. Fierro at the Institute of Catalysis and Petrochemistry (CSIC). From 1990 to 1993, he was working under contract in a project of oxidative coupling of methane funded by REPSOL (the largest Spanish oil and petrochemisty company). At the end of this period, he got a staff position of researcher in the Institute of Catalysis and Petrochemisty, that is his current status. In 1996−1997, he was a Visiting Scholar in the group of Prof. A. Varma, at the University of Notre Dame (USA). He has been the Head of the Department of Sturcture and Reactivity of the Institute of Catalysis and Petrochemistry since 1998. His research interests are focused mainly in catalytic processes for clean energy production, specifically in catalytic applications of perovskite oxides (Ph.D. dissertation), natural gas conversion, catalytic combustion, C 1 chemistry, catalyic membrane reactors, hydrogen production, and fuel cell catalysts. He has published 30 papers and 3 patents and made 22 presentations at symposia and conferences.
“…NO coverage on all these oxides were found to be of the same order of magnitude as those measured for the simple oxides . The infrared spectra of NO adsorbed on the manganite LaMnO 3 showed bands of dinitrosyls and nitrite and nitrate species . This finding indicates that NO molecule interacts either through Mn 3+ ions (dinitrosyls) or through O 2- ions (nitrite and nitrates) as illustrated in the scheme: …”
Section: Co and No Adsorptionmentioning
confidence: 53%
“…48 The infrared spectra of NO adsorbed on the manganite LaMnO 3 showed bands of dinitrosyls and nitrite and nitrate species. 47 This finding indicates that NO molecule interacts either through Mn 3+ ions (dinitrosyls) or through O 2ions (nitrite and nitrates) as illustrated in the scheme: Successive NO-CO and CO-NO adsorptions on LaMO 3 at 298 K showed an inhibiting effect of NO on subsequent CO adsorption, and this was larger than the inhibiting effect of CO on NO adsorption. 39 NO adsorbs more strongly than CO, in accordance with previous observations by Yao and Shelef 48 for other perovskites.…”
Section: Co and No Adsorptionmentioning
confidence: 94%
“…This observation suggests that the nature of the adsorption is not altered with temperature. For LaCrO 3 , LaMnO 3 , and LaRhO 3 , the temperature interval where NO adsorption changes moderately (below 20%) was narrower. NO coverage on all these oxides were found to be of the same order of magnitude as those measured for the simple oxides .…”
Section: Co and No Adsorptionmentioning
confidence: 94%
“…Consistent with this, comparison of the thermodynamic parameters for the adsorption of NO and CO on LaCrO 3 revealed higher adsorption enthalpy and lower adsorption entropy for NO than for CO. The almost constancy of the amounts of adsorbed NO with temperature as well as the strength of the NO-surface bond are arguments in favor of the use of NO instead CO for determining metallic sites. ,,,, However, the complex IR spectra of chemisorbed NO 39,42,45 indicate that there is no specificity for the adsorption on metal or cation sites, and, therefore, the assumption of a 1:1 stoichiometry between NO and B 3+ sites may not give a proper estimate of the density of surface transition-metal sites. Thus, the CO molecule, whose interaction with B 3+ ions is weaker than with NO at temperatures close to ambient, is recommended for evaluating B 3+ cations in perovskite oxides.…”
He obtained his Ph.D. in chemistry in 1990 at the same university, working under the supervision of Dr. L. Gonza ´lez Tejuca and Prof. J. L. G. Fierro at the Institute of Catalysis and Petrochemistry (CSIC). From 1990 to 1993, he was working under contract in a project of oxidative coupling of methane funded by REPSOL (the largest Spanish oil and petrochemisty company). At the end of this period, he got a staff position of researcher in the Institute of Catalysis and Petrochemisty, that is his current status. In 1996−1997, he was a Visiting Scholar in the group of Prof. A. Varma, at the University of Notre Dame (USA). He has been the Head of the Department of Sturcture and Reactivity of the Institute of Catalysis and Petrochemistry since 1998. His research interests are focused mainly in catalytic processes for clean energy production, specifically in catalytic applications of perovskite oxides (Ph.D. dissertation), natural gas conversion, catalytic combustion, C 1 chemistry, catalyic membrane reactors, hydrogen production, and fuel cell catalysts. He has published 30 papers and 3 patents and made 22 presentations at symposia and conferences.
“…[Tascon J.M.D., Tejuca L.G., Rochester C.H., 1985, Tascon J.M.D., Tejuca L.G.Z., 1980, Pena M.A., Tascon J.M.D., Fierro J.M.D., Tejuca L.G.J., 1987, Tejuca L.G., Bell A.T., Fierro J.L.G., Tascon J.M.D., 1987, Tejuca L.G., Bell A.T., Fierro J.L.G., Pena M.A., 1988. [Pena M.A., Tascon J.M.D., Fierro J.M.D., Tejuca L.G., 1987] και LaRhO 3.47 [Tascon J.M.D., Olivan A.M.O., Tejuca L.G., 1986] η θερμοκρασιακή περιοχή όπου η προσρόφηση του ΝΟ παραμένει σταθερή ή αλλάζει σε μέτριο βαθμό (κάτω από 20%) είναι πιο περιορισμένη. Η κάλυψη της επιφάνειας σε όλα τα οξείδια της σειράς LaBO 3 βρέθηκε διαφορετική σε σύγκριση με τα απλά οξείδια ΒΟ Χ [Yao H.C., Shelef M., 1974].…”
Τα άτομα Ti είναι τοποθετημένα στις κορυφές και τα άτομα Sr στο κέντρο του κύβου (σχήμα 1.1c). Τα άτομα οξυγόνου βρίσκονται τοποθετημένα στα κέντρα των δώδεκα ακμών του κύβου, σχηματίζοντας οκτάεδρα του τύπου TiO 6 τα οποία εκτείνονται απείρως σε τρεις διαστάσεις. Τα σχηματιζόμενα TiO 6 οκτάεδρα είναι τέλεια με έξι ίσους δεσμούς Ti-O = α/2 = 1.952 Å, υπό γωνία 90 0 , όπου α είναι το μήκος της ακμής μιας κυψελίδας. Κάθε άτομο Sr περιβάλλεται από δώδεκα ισαπέχοντα άτομα οξυγόνου σε απόσταση ίση με το ήμισυ της διαγωνίου της κάθε κυψελίδας, δηλαδή με r Sr-O = α√2/2 = 2.761 Å [A.S. Bhalla, Ruyan Guo, Rustum Roy, 2000]. Στον επόμενο πίνακα παρουσιάζονται χαρακτηριστικά μήκη ακμών της κυψελίδας διαφόρων περοβσκιτών. Πίνακας 1.1 Περοβσκίτες και μήκη των ακμών της κυψελίδας αυτών.
ΠεροβσκίτηςΜήκος κυβικής κυψελίδας α (Å) CaTiO 3 3.80 ± 0.02 SrTiO 3 3.92 ± 0.02 BaTiO 3 3.97 ± 0.02 KIO 3 4.46 ± 0.02 RbIO 3 4.52 ± 0.02 NaNbO 3 3.98 ± 0.02 KNbO 3 4.01 ± 0.02 CaZrO 3 3.99 ± 0.10 Σχήμα 1.1 (a) Η ιδανική περοβσκιτική φάση για το SrTiO 3 όπου τα οκτάεδρα εκτείνονται σε τρεις διαστάσεις. (b) και (c) άλλοι τρόποι παρουσίασης της περοβσκιτικής δομής [A.S. Bhalla, Ruyan Guo, Rustum Roy, 2000]. ΔΕΙΓΜΑ ΤΥΠΟΣ ΣΥΜΜΕΤΡΙΑΣ Τετραγωνική /Μονοκλινής (n=1) La n+1 Ni n O 3n+1 (n=1, 2, 3) Ορθορομβική (n=2, 3) Ορθορομβική (n=1, 3
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