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Titolo:
Epoxidation of styrene on Si/Ti/SiO2 catalysts prepared by chemical grafting
Autore:
Yang, QH; Wang, SL; Lu, JQ; Xiong, G; Feng, ZC; Xin, Q; Li, C;
Indirizzi:
Chinese Acad Sci, Dalian Inst Chem Phys, State Key Lab Catalysis, Dalian 116023, Peoples R China Chinese Acad Sci Dalian Peoples R China 116023 n 116023, Peoples R China
Titolo Testata:
APPLIED CATALYSIS A-GENERAL
, volume: 194, anno: 2000,
pagine: 507 - 514
SICI:
0926-860X(20000313)194:<507:EOSOSC>2.0.ZU;2-G
Fonte:
ISI
Lingua:
ENG
Soggetto:
SILICA MIXED OXIDES; TITANIUM TETRACHLORIDE; SURFACES; HYDROPEROXIDES; CYCLOHEXENE; OLEFINS; TICL4; BETA;
Keywords:
chemical grafting; titanium-silica; epoxidation; UV resonance Raman; visible Raman; styrene;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Engineering, Computing & Technology
Citazioni:
30
Recensione:
Indirizzi per estratti:
Indirizzo: Li, C Chinese Acad Sci, Dalian Inst Chem Phys, State Key Lab Catalysis, Dalian 116023, Peoples R China Chinese Acad Sci Dalian Peoples R China 116023 23, Peoples R China
Citazione:
Q.H. Yang et al., "Epoxidation of styrene on Si/Ti/SiO2 catalysts prepared by chemical grafting", APP CATAL A, 194, 2000, pp. 507-514

Abstract

Titania-silica (Ti/SiO2) and silica-titania-silica (Si/Ti/SiO2) catalysts were:prepared by chemical grafting using TiCl4 and tetraethyl orthosilicate(TEOS) as precursors and SiO2 as support. The prepared catalysts were characterized by UV Raman and visible Raman spectroscopies, XRD and the epoxidation of styrene; Ti/SiO2: catalyst grafted with only titanium species is not very active for epoxidation using H2O2 (30%), but is active and-selectivewhen one uses tert-butyl hydroperoxide (TBHP). The catalyst grafted at high temperatures shows better epoxide selectivity. Si/Ti/SiO2 catalyst, the titanium-silica grafted further with TEOS, is active and selective for the epoxidation of styrene using either dilute H2O2 or TBHP, possibly due to thefact that the grafting of Ti/SiO2 with TEOS modifies the coordination structure of titanium and makes the titanium sites of Si-O-Ti-O-Si species lesshydrophilic. A characteristic band at 1085cm(-1) due to Ti-O-Si species isdetected for the grafted catalysts by UV resonance Raman spectroscopy. Reaction between TiCl4 and SiO2 at high temperatures favors the formation of Ti-O-Si species. Better activity and selectivity to epoxide,is found for thecatalysts with more Ti-O-Si species. It is assumed that the active sites are the highly isolated Ti-O-Si species. For Si/Ti/SiO2 catalyst, the gas phase O-2 can participate in the catalytic oxidation of styrene when H2O2 is present ana:ii causes the formation of benzaldehyde. (C) 2000 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 29/11/20 alle ore 00:59:58