Grafting of Molecularly Ordered Mesoporous Phenylene-Silica with Molybdenum Carbonyl Complexes: Efficient Heterogeneous Catalysts for the Epoxidation of Olefins

authors	Coelho, AC; Balula, SS; Bruno, SM; Alonso, JC; Bion, N; Ferreira, P; Pillinger, M; Valente, AA; Rocha, J; Goncalves, IS
nationality	International
journal	ADVANCED SYNTHESIS & CATALYSIS
author keywords	epoxidation; heterogeneous catalysis; molybdenum; periodic mesoporous organosilicas; supported catalysts
keywords	LIMONENE EPOXIDATION; SCALE PERIODICITY; BENZENE-SILICA; PORE-SIZE; SELECTIVE OXIDATION; ORGANOSILICAS PMOS; HYDROGEN-PEROXIDE; HYBRID MATERIALS; ORGANIC GROUPS; MCM-41
abstract	Arenetricarbonyl complexes, or the general formula -C(6)H(4)Mo(CO)(3)-, were incorporated into crystal-like mesoporous phenylene-silica by liquid-phase deposition of molybdenum hexacarbonyl [Mo(CO)(6)]. By adjusting the reaction conditions, different molybdenum loadings of 1.5 and 5.9 wt% were obtained, which correspond to 3% and 14% of the phenylene contents. The texture properties of the materials as well as the nature of the surface-fixed complexes were characterized by powder X-ray diffraction, transmission electron microscopy (TEM), N(2) adsorption, FT-IR. UV-vis and MAS ((13)C, (29)Si) NMR spectroscopy. The derivatized organosilicas were examined as catalyst precursors for the liquid-phase epoxidation of cis-cyclooctene, 1-octene, trans-2-octene and (R)-(+)-limonene at 55 degrees C, using tert-butyl hydroperoxide as the oxidant. For each olefin the corresponding epoxide was the only product detected. In the case of cyclooctene, the intrinsic reaction rates per surface molybdenum atom were similar for both Mo loadings (TOF similar to 1150 mol mol(Mo)(1) h(-1)), suggesting that the resultant materials act as single site epoxidation catalysts. Leaching tests and metal analyses of reaction solutions showed that the catalytic activity stemmed from the immobilized species and not from the leaching of active species into solution. The oxidation of limonene gave limonene oxide as the only product in 95% yield at 3 h. which reveals an outstanding regioselectivity to the epoxidation of the endocyclic double bond.
publisher	WILEY-V C H VERLAG GMBH
issn	1615-4150
year published	2010
volume	352
issue	10
beginning page	1759
ending page	1769
digital object identifier (doi)	10.1002/adsc.201000042
web of science category	Chemistry, Applied; Chemistry, Organic
subject category	Chemistry
unique article identifier	WOS:000280657900029