Complexation of crystal-like mesoporous phenylene-silica with Cr(CO)(3) and catalytic performance in the oxidation of cyclooctene

authors	Coelho, AC; Balula, SS; Antunes, MM; Gerganova, TI; Bion, N; Ferreira, P; Pillinger, M; Valente, AA; Rocha, J; Goncalves, IS
nationality	International
journal	JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL
author keywords	Periodic mesoporous organosilicas; Supported catalysts; Chromium; Decarbonylation; Epoxidation
keywords	CHROMIUM CARBONYL-COMPLEXES; T-BUTYL HYDROPEROXIDE; VIBRATIONAL SPECTROSCOPY; HETEROGENEOUS CATALYSTS; MOLECULAR-SCALE; HYBRID MATERIAL; HYDROGENATION; TRICARBONYL; OLEFINS; FTIR
abstract	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.
publisher	ELSEVIER SCIENCE BV
issn	1381-1169
year published	2010
volume	332
issue	1-2
beginning page	13
ending page	18
digital object identifier (doi)	10.1016/j.molcata.2010.08.010
web of science category	Chemistry, Physical
subject category	Chemistry
unique article identifier	WOS:000284674300003