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Titolo:
Infrared and volumetric study of NO adsorption on Pd-H-ZSM-5
Autore:
Pommier, B; Gelin, P;
Indirizzi:
Univ Lyon 1, CNRS, UMR 5634, Lab Applicat Chim Environm, F-69622 Villeurbanne, France Univ Lyon 1 Villeurbanne France F-69622 nm, F-69622 Villeurbanne, France
Titolo Testata:
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
fascicolo: 6, volume: 3, anno: 2001,
pagine: 1138 - 1143
SICI:
1463-9076(2001)3:6<1138:IAVSON>2.0.ZU;2-3
Fonte:
ISI
Lingua:
ENG
Soggetto:
EXCHANGED ZSM-5 CATALYSTS; NITROGEN MONOXIDE; NITRIC-OXIDE; SELECTIVE REDUCTION; 2133 CM(-1); METHANE; OXYGEN; PD; ZEOLITES; H-ZSM-5;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
20
Recensione:
Indirizzi per estratti:
Indirizzo: Gelin, P Univ Lyon 1, CNRS, UMR 5634, Lab Applicat Chim Environm, 43 Blvd 11 Novembre 1918, F-69622 Villeurbanne, France Univ Lyon 1 43 Blvd 11 Novembre 1918 Villeurbanne France F-69622
Citazione:
B. Pommier e P. Gelin, "Infrared and volumetric study of NO adsorption on Pd-H-ZSM-5", PHYS CHEM P, 3(6), 2001, pp. 1138-1143

Abstract

The adsorption of NO on Pd-exchanged H-ZSM-5 containing from 0.18 up to 1.56 wt.% Pd was studied by in situ FTIR spectroscopy and dynamic volumetric experiments. At room temperature, NO adsorbs as two distinct NO-containing species (nu (NO) at 2136 and 1881 cm(-1)). These species exhibit different thermal stability: the 2136 cm(-1) species easily decomposes in vacuo below473 K while the 1881 cm(-1) species is stable up to 673 K. At 523 K in flowing NO, only the 1881 cm(-1) species forms and NO2 is released. The striking feature is that the release of NO2 is delayed with respect to the NO consumption and that, after being formed, NO2 is reversibly adsorbed with NO in a 1:1 ratio inside the channels of the zeolite. By combining mass spectrometry, IR spectroscopy and volumetric data, the transient species were unambiguously associated with the 2136 cm(-1) species and attributed to NO+ occupying exchange sites. All these data were consistent with the reduction ofPd(II) into Pd(I) ions dispersed in the zeolite channels and the subsequent formation of Pd(I) mononitrosyl complexes responsible for the 1881 cm(-1)feature. The Pd(I) nitrosyl complexes are monovalent and strongly anchoredto the zeolite framework, as indicated by the appearance of a sharp IR band at 975 cm(-1) attributed to distorted T-O (T=Si, Al) vibrations. The dispersion of Pd as isolated complexes at exchange sites in the zeolite channels was found to depend strongly on both Pd loading and activation conditions.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 07/07/20 alle ore 12:39:01