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Titolo:
Characterization of active sites on AgHf2(PO4)(3) in butan-2-ol conversion
Autore:
Brik, Y; Kacimi, M; Bozon-Verduraz, F; Ziyad, M;
Indirizzi:
Fac Sci, Dept Chim, Lab Physicochim Mat & Catalyse, Rabat, Morocco Fac Sci Rabat Morocco m, Lab Physicochim Mat & Catalyse, Rabat, Morocco Univ Paris 07, Lab Chim Mat Divises & Catalyse, F-75251 Paris, France UnivParis 07 Paris France F-75251 ses & Catalyse, F-75251 Paris, France
Titolo Testata:
MICROPOROUS AND MESOPOROUS MATERIALS
fascicolo: 1, volume: 43, anno: 2001,
pagine: 103 - 112
SICI:
1387-1811(200103)43:1<103:COASOA>2.0.ZU;2-4
Fonte:
ISI
Lingua:
ENG
Soggetto:
DIFFUSE-REFLECTANCE SPECTROSCOPY; SILVER-CLUSTER FORMATION; SELECTIVE OXIDATION; ETHYLENE-OXIDE; CATALYSTS; NASICON; PHOSPHATE; DECOMPOSITION; MECHANISM; BEHAVIOR;
Keywords:
silver-hafnium phosphate; supported silver; butan-2-ol conversion; dynamic diffuse reflectance spectroscopy;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
25
Recensione:
Indirizzi per estratti:
Indirizzo: Ziyad, M Fac Sci, Dept Chim, Lab Physicochim Mat & Catalyse, Ave Ibn Battouta,BP 1014, Rabat, Morocco Fac Sci Ave Ibn Battouta,BP 1014 Rabat Morocco , Rabat, Morocco
Citazione:
Y. Brik et al., "Characterization of active sites on AgHf2(PO4)(3) in butan-2-ol conversion", MICROP M M, 43(1), 2001, pp. 103-112

Abstract

The silver-hafnium phosphate (AgHf2(PO4)(3)), belonging to the Nasicon-type structure, was synthesized by a sol-gel method and characterized by several techniques. The Ag+ cations were found to be, as in zeolite frameworks, easy to reduce to metallic silver. This reduction was investigated by STEM/EDX which showed that, under an intense electron beam, the Ag+ ions diffusetoward the surface of the sample and form metallic particles of sizes varying from 3 to 15 nm, The X-ray diffraction patterns confirmed that the reduction does not damage the phosphate structure, The Ag+ ions were replaced in the structure by protons giving rise to (PO-H) acid groups. The catalytic behavior of AgHf2(PO4)(3) was studied in butan-2-ol conversion. In the absence of O-2, the reaction leads to an abrupt decrease of the dehydrogenation activity and a dehydration reaction that reaches a pseudo-stationary state. Concomittantly, the Ag+ cations are reduced to Ag-0. In the presence of O-2, the dehydrogenation reaction undergoes a complex transitory state which can be decomposed into two steps. During the first one, theactivity decreases in concert with the reduction of Ag+ ions. Tn the second step it increases as the amount of oxidized silver species (AgxOy), whichare the active sites for the alcohol dehydrogenation, increases. UV-VIS characterization of AgHf2(PO4)(3) in dynamic conditions similar to those used in the catalytic tests confirmed that butan-2-ol reduces Ag+ ions to metallic silver which, in the presence of O-2 in the reaction mixture,are oxidized to (AgxOy). (C) 2001 Elsevier Science B.V. All rights reserved.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 29/03/20 alle ore 15:38:57