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Titolo:
Characterization of Cr2+ and ethylene polymerization on Cr/SiO2 catalysts
Autore:
Gaspar, AB; Martins, RL; Schmal, M; Dieguez, LC;
Indirizzi:
Univ Fed Rio de Janeiro, NUCAT, PEQ, COPPE, BR-21945970 Rio De Janeiro, Brazil Univ Fed Rio de Janeiro Rio De Janeiro Brazil BR-21945970 BCeiro, Brazil
Titolo Testata:
JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL
fascicolo: 1-2, volume: 169, anno: 2001,
pagine: 105 - 112
SICI:
1381-1169(20010328)169:1-2<105:COCAEP>2.0.ZU;2-M
Fonte:
ISI
Lingua:
ENG
Soggetto:
DIFFUSE-REFLECTANCE SPECTROSCOPY; SUPPORTED CHROMIUM CATALYSTS; OXIDE CATALYSTS; SILICA; COORDINATION; IONS; IR;
Keywords:
Cr/SiO2; TPR; FT-IR; ethylene polymerization;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
22
Recensione:
Indirizzi per estratti:
Indirizzo: Dieguez, LC Univ Fed Rio de Janeiro, NUCAT, PEQ, COPPE, CP 68502, BR-21945970 Rio De Janeiro, Brazil Univ Fed Rio de Janeiro CP 68502 Rio De JaneiroBrazil BR-21945970 BC
Citazione:
A.B. Gaspar et al., "Characterization of Cr2+ and ethylene polymerization on Cr/SiO2 catalysts", J MOL CAT A, 169(1-2), 2001, pp. 105-112

Abstract

Cr/SiO2 catalysts were prepared by impregnation of chromium acetate (1 and3 wt.% Cr) and bis(triphenylsilyl)chromate (0.5 wt.% Cr) over commercial silica. These samples were analyzed by temperature programmed reduction (TPR) and infrared spectroscopy (FT-IR) of CO and C2H4 adsorbed in order to characterize the chromium species, mainly Cr2+ species distribution (Cr-A(2+),Cr-B(2+) and Cr-C(2+)) and polymerization aspects. The catalysts prepared with chromium acetate presented only Cr6+ after calcination, while the catalyst prepared with bis(triphenylsilyl)chromate presented Cr6+ and a fraction of Cr3+. After reduction with CO, the catalysts prepared with chromium acetate showed more Cr-B(2+) than Cr-A(2+) species. The distribution of Cr2+ species influenced the catalytic activity. The catalyst with 3 wt.% Cr fromacetate presented the greatest amount of species Cr-A(2+) and Cr-B(2+) andthe best polymerization activity. The behavior of isolated hydroxyls band during polymerization tests, characterized by FT-IR, suggests its participation in the reaction mechanism. (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 02/04/20 alle ore 05:51:36