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Titolo:
Variability in the structure of supported MoO3 catalysts: Studies using Raman and X-ray absorption spectroscopy with ab initio calculations
Autore:
Radhakrishnan, R; Reed, C; Oyama, ST; Seman, M; Kondo, JN; Domen, K; Ohminami, Y; Asakura, K;
Indirizzi:
Virginia Polytech Inst & State Univ, Dept Chem Engn, Environm Catalysis & Mat Lab, Blacksburg, VA 24061 USA Virginia Polytech Inst & State Univ Blacksburg VA USA 24061 VA 24061 USA Virginia Polytech Inst & State Univ, Dept Chem, Blacksburg, VA 24061 USA Virginia Polytech Inst & State Univ Blacksburg VA USA 24061 VA 24061 USA Tokyo Inst Technol, Lab Nat Resources Utilizat, Midori Ku, Yokohama, Kanagawa 2268503, Japan Tokyo Inst Technol Yokohama Kanagawa Japan 2268503 anagawa 2268503, Japan Hokkaido Univ, Catalysis Res Ctr, Sapporo, Hokkaido 0600811, Japan Hokkaido Univ Sapporo Hokkaido Japan 0600811 oro, Hokkaido 0600811, Japan
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY B
fascicolo: 36, volume: 105, anno: 2001,
pagine: 8519 - 8530
SICI:
1520-6106(20010913)105:36<8519:VITSOS>2.0.ZU;2-T
Fonte:
ISI
Lingua:
ENG
Soggetto:
MOLYBDENUM OXIDE CATALYSTS; JRC-REFERENCE CATALYSTS; FINE-STRUCTURE; ELECTRONIC-STRUCTURE; ETHANOL OXIDATION; SILICA CATALYSTS; ALUMINA CATALYST; L(3)-EDGE XANES; BINARY OXIDES; SURFACE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
45
Recensione:
Indirizzi per estratti:
Indirizzo: Asakura, K Virginia Polytech Inst & State Univ, Dept Chem Engn, Environm Catalysis & Mat Lab, Blacksburg, VA 24061 USA Virginia Polytech Inst & StateUniv Blacksburg VA USA 24061 SA
Citazione:
R. Radhakrishnan et al., "Variability in the structure of supported MoO3 catalysts: Studies using Raman and X-ray absorption spectroscopy with ab initio calculations", J PHYS CH B, 105(36), 2001, pp. 8519-8530

Abstract

Molybdenum oxide catalysts (1 wt %) supported on SiO2 (L-90, 95 m(2)/g), SiO2 (EH-5, 350 m(2)/g), Al2O3 (96 m(2)/g), and TiO2 (52 m(2)/g) were characterized using Raman spectroscopy and near-edge and extended X-ray absorption fine structure (NEXAFS and EXAFS, respectively) spectroscopies. The structural possibilities (tetrahedral and distorted octahedral) for the Mo active center were explored using ab initio calculations through the Hartree-Fock method using a 3-21G(d) basis set. The Raman vibrational frequencies and bond lengths obtained from EXAFS were compared to ab initio calculations toarrive at the likely structures for the isolated Mo centers on each support. The studies revealed a mixture of tetrahedral Mo sites along with crystalline MoO3 for the MoO3/SiO2 (L-90) catalyst. The Mo sites for the MoO3/SiO2 (EH-5) catalyst were found to be a mixture of isolated, tetrahedral, and distorted octahedral sites. The MoO3/Al2O3 catalyst was found to have isolated, tetrahedral sites. Finally, the MoO3/TiO2 catalyst was found to have distorted octahedral Mo active centers. Complementary information from Raman, NEXAFS, and EXAFS spectra and ab initio calculations were required to arrive at the structural assignments for the Mo centers in the present study. Importantly, however, the calculations indicate the possible existence of other stable geometries and help explain the many diverging conclusions in the literature concerning the structure of supported molybdenum oxide catalysts.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 19/09/20 alle ore 18:44:35