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Titolo:
Study of adsorption and reactions of methyl iodide on TiO2
Autore:
Su, C; Yeh, JC; Chen, CC; Lin, JC; Lin, JL;
Indirizzi:
Acad Sinica, Inst Atom & Mol Sci, Taipei 106, Taiwan Acad Sinica Taipei Taiwan 106 a, Inst Atom & Mol Sci, Taipei 106, Taiwan Natl Cheng Kung Univ, Dept Chem, Tainan 701, Taiwan Natl Cheng Kung Univ Tainan Taiwan 701 iv, Dept Chem, Tainan 701, Taiwan
Titolo Testata:
JOURNAL OF CATALYSIS
fascicolo: 1, volume: 194, anno: 2000,
pagine: 45 - 54
SICI:
0021-9517(20000815)194:1<45:SOAARO>2.0.ZU;2-M
Fonte:
ISI
Lingua:
ENG
Soggetto:
POWDERED TIO2; ALIPHATIC-ALCOHOLS; TIO2(110) SURFACES; TITANIUM DIOXIDES; SINGLE-CRYSTAL; OXIDE; PHOTOCATALYSIS; DISSOCIATION; OXIDATION; CHEMISTRY;
Keywords:
methyl iodide; TiO2; thermal reaction; photochemistry; powder; single crystal; FT-IR; XPS; TPD;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Engineering, Computing & Technology
Citazioni:
59
Recensione:
Indirizzi per estratti:
Indirizzo: Lin, JL Acad Sinica, Inst Atom & Mol Sci, POB 23-166, Taipei 106, Taiwan Acad Sinica POB 23-166 Taipei Taiwan 106 -166, Taipei 106, Taiwan
Citazione:
C. Su et al., "Study of adsorption and reactions of methyl iodide on TiO2", J CATALYSIS, 194(1), 2000, pp. 45-54

Abstract

The adsorption, thermal reactions, and photochemistry of methyl iodide were studied on powdered TiO2 by transmission infrared spectroscopy, and on a TiO2(110) single-crystal surface by temperature-programmed desorption (TPD)and X-ray photoemission spectroscopy (XPS). CH3I is either adsorbed molecularly or adsorbed dissociatively, forming methoxy groups on powdered TiO2 by thermal activation as observed by IR spectroscopy. The dissociation of CH3I is enhanced by the presence of surface hydroxyl groups. CH4(g) evolves thermally as a major product when CH3I reacts with powdered TiO2 in the absence of oxygen. However, only oxygen-containing reaction intermediates and products are found when oxygen is present, including CH2O(g), (CH3)(2)O-(g),CO2(g), CO2(g), and H2O(g). (CH3)(2)O-(g) is formed via a coupling reaction of two adsorbed methoxy groups. For the thermal reactions on TiO2(110), desorption of (CH3)(2)O-(g) is observed at multilayer coverages by TPD study. The formation of (CH3)(2)O-(g) On TiO2(110) occurs at much lower temperatures. It starts to evolve at similar to 200 K and reaches its maximum rate at 250-330 K depending on surface heterogeneity in the TPD study. The Williamson synthesis process is proposed for the generation of (CH3)(2)O-(g) in this case. In addition, surface iodine formed by X-ray irradiation on CH3I-covered TiO2 is not stable and is desorbed by 570 K. In the photochemistry of CH3I over powdered TiO2, when O-2 is absent, negligible reactions occur. In the presence of O-2, some CH3I is photooxidizcd to surface formate groups and CO2(g). This reaction is most likely initiated by superoxide, O-2(-), formed upon irradiation. (C) 2000 Academic Press.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 30/03/20 alle ore 12:58:20