resumo
Chromium carbonyl complexes were incorporated into a molecularly ordered mesoporous phenylene-silica by reaction with Cr(CO)(6) in refluxing 1,2-dichloroethane (DCE). The modified material with a chromium loading of 0.07 mmol g(-1) was characterised by powder X-ray diffraction, N-2 adsorption, thermogravimetric analysis (TGA), FT-IR, C-13 and Si-29 MAS NMR spectroscopies. TGA under air indicated that thermal decarbonylation between 250 and 350 degrees C preceded the Cr-promoted decomposition and release of organic fragments at a lower temperature (onset ca. 380 degrees C) than that registered for the phenylene-silica precursor (onset ca. 550 degrees C). The catalytic performance of the modified phenylene-silica was evaluated in the oxidation of cis-cyclooctene at 55 degrees C with tert-butylhydroperoxide (TBHP) as the oxidant and DCE as the co-solvent. The main product was the epoxide, formed in 83% yield after 24 h, with 2-cycloocten-1-one being the main by-product. Although the activity of the catalyst decreased after the first recycle, possibly clue to partial chromium leaching, it remained nearly the same thereafter, and leaching tests indicated that the catalytic reaction was essentially heterogeneous in nature. Tests carried out using a radical scavenger indicated that the reaction of the olefin with TBHP may involve both free radical and non-radical reaction mechanisms. (C) 2010 Elsevier B.V. All rights reserved.
palavras-chave
CHROMIUM CARBONYL-COMPLEXES; T-BUTYL HYDROPEROXIDE; VIBRATIONAL SPECTROSCOPY; HETEROGENEOUS CATALYSTS; MOLECULAR-SCALE; HYBRID MATERIAL; HYDROGENATION; TRICARBONYL; OLEFINS; FTIR
categoria
Chemistry
autores
Coelho, AC; Balula, SS; Antunes, MM; Gerganova, TI; Bion, N; Ferreira, P; Pillinger, M; Valente, AA; Rocha, J; Goncalves, IS
nossos autores
Anabela Tavares Aguiar Valente
Investigador Principal
Isabel Maria de Sousa Gonçalves
Professor associado
João Rocha
Prof. Catedrático
Maria Margarida Feitor Pintão Moreno Antunes
Investigador Júnior
Martyn Pillinger
Investigador Principal
Paula Celeste da Silva Ferreira
Investigador CoordenadorGrupos
G1 - Materiais Porosos e Nanossistemas
G2 - Materiais Fotónicos, Eletrónicos e Magnéticos
G4 - Materiais Renováveis e Economia Circular
Projectos
Periodic mesoporous organic-inorganic hybrids (POCI/CTM/55648/2004)
RMNE-UA-National Network of Electron Microscopy (REDE/1509/RME/2005 )
agradecimentos
The authors are grateful to the Fundacao para a Ciencia e a Tecnologia (FCT), POCI 2010, OE and FEDER (Projects POCI/CTM/55648/2004 and PPCDT/CTM/55648/2004), and to RNME (Project FCT: REDE/1509/RME/2005) for financial support. The FCT is acknowledged for PhD grants to A.C.C. and M.M.A.