Actas de congresos
Molybdenum-based Epoxidation Catalysts Heterogenized In Silica Matrixes Via The Sol-gel Method
Registro en:
Journal Of Molecular Catalysis A: Chemical. , v. 182-183, n. , p. 167 - 173, 2002.
13811169
10.1016/S1381-1169(01)00459-9
2-s2.0-0037205206
Autor
Teixeira S.
Dallmann K.
Schuchardt U.
Buffon R.
Institución
Resumen
MoO2 (acac)2 has been encapsulated in silica matrixes prepared by hydrolysis/condensation of tetraethylorthosilicate. Alternatively, hybrid organic-inorganic matrixes were prepared by adding 3-(triethoxysilyl)propylethylenediamine or 1,4-bis(tri-ethoxysilyl)benzene to the reaction mixture. All systems were tested in the epoxidation of cyclohexene or cis-cyclooctene at 70 °C using tert-butyl hydroperoxide as the oxidant. In most experiments, 1,2-dichloroethane as a solvent and a molar ratio of [Mo]:[TBHP]:[olefin] = 1:130:130 were employed. The catalysts immobilized in inorganic matrixes prepared in acidic conditions showed high activity in the first run, which could be attributed to the occurrence of homogeneous catalysis; basic conditions led to a significant decrease in activity with a concomitant decrease in the specific surface area of the matrix. Hybrid systems were less active in the first run, but their activities remained almost constant in at least four consecutive runs. Selectivities for epoxides were higher than 97% in all the cases. © 2002 Elsevier Science B.V. All rights reserved. 182-183
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