Dioxomolybdenum(VI) modified mesoporous materials for the catalytic epoxidation of olefins
authors Bruno, SM; Fernandes, JA; Martins, LS; Goncalves, IS; Pillinger, M; Ribeiro-Claro, P; Rocha, J; Valente, AA
nationality International
journal CATALYSIS TODAY
author keywords chelating ligands; dioxomolybdenum(VI) complexes; epoxidation; mesoporous materials; molybdenum supported catalysts
keywords MOLYBDENUM COMPLEXES; MOLECULAR-SIEVES; MCM-41 MATERIALS; LEWIS-BASE; CYCLOOCTENE; OXIDATION; HETEROGENIZATION; ADSORPTION
abstract Organic-inorganic hybrid heterogeneous catalyst systems were synthesized by the reaction of the dioxomolybdenum(VI) complex MoO(2)Cl(2)(THF)(2) with the mesoporous silica MCM-41 functionalized with a pyrazolylpyridine ligand (MCM-41-PP). Two catalysts were prepared, one of which involved the postsynthesis trimethylsilylation of MCM-41-PP to remove the residual surface silanol groups. The model complex MoO(2)Cl(2)L {L =ethyl [3-(2-pyridyl)-1-pyrazolyl] acetate} was also synthesized. Elemental analysis of the supported mesoporous materials indicated molybdenum loadings of 8.0 wt.% (0.83 mmol g(-1)) for MCM-41-PP-MoO(2)Cl(2) and 7.0 wt.% (0.73 mmol g(-1)) for silylated MCM-41-PP(.)MoO(2)Cl(2). The supported materials were further characterized by N(2) adsorption, (13)C/(29)Si (CP) MAS NMR, IR and Raman spectroscopy. The spectroscopic data are consistent with the successful formation of tethered complexes of the type MoO(2)Cl(2)(PP), although the materials also contained an excess of dioxomolybdenum(VI) species that were probably not coordinated directly with the surface-bound ligands. The modified materials are active and selective in the epoxidation of cyclooctene at 328 K using t-BuOOH (in decane) as the oxidant and no additional solvent. The initial specific reaction rates were about 350 mol mol(Mo)(-1) h(-1) for the modified materials and also the model complex MoO(2)Cl(2)L. Stability was checked by recycling the solid catalysts several times. Some activity is lost from the first to second runs, but thereafter stabilizes. The catalytic performance of the hybrid materials was further investigated in the oxidation of at-pinene, (R)-(+)-limonene, trans-2-octene and 1-octene. (c) 2006 Elsevier B.V. All rights reserved.
publisher ELSEVIER SCIENCE BV
issn 0920-5861
year published 2006
volume 114
issue 2-3
beginning page 263
ending page 271
digital object identifier (doi) 10.1016/j.cattod.2006.01.007
web of science category Chemistry, Applied; Chemistry, Physical; Engineering, Chemical
subject category Chemistry; Engineering
unique article identifier WOS:000237735300020
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journal impact factor 5.825
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