resumo
A series of tetrabutylammonium (TBA) salts of the transition metal mono-substituted silicotungstates [SiW11M(H2O)O-39](n-), M = Co-II, Fe-III, Mn-III, (SiW11M) were explored as homogeneous catalysts for the oxidation of geraniol and styrene with H2O2. The most active homogeneous catalysts (SiW11Co and SiW11Fe) were immobilized onto an amine-functionalized SBA-15 (aptesSBA-15) and the resulting composites were characterized using several techniques (FT-IR, FT-Raman, UV-Vis/DRS, elemental analysis, powder XRD, SEM and N-2 adsorption-desorption isotherms). The catalytic performance of the new composites SiW11Co@aptesSBA-15 and SiW11Fe@aptesSBA-15 was investigated under similar experimental conditions to those used for homogeneous counterparts. 2,3-Epoxygeraniol and benzaldehyde were the main products obtained from geraniol and styrene oxidation, respectively, for all the catalysts. SiW11Co and SiW11Co@aptesSBA-15 showed to be the most active catalysts for the oxidation of geraniol and styrene. The recyclability of the composite SiW11Co@aptesSBA-15 was investigated for three reaction cycles. The stability of the composites was confirmed using several techniques after catalytic cycles.
palavras-chave
IRON-SUBSTITUTED POLYOXOTUNGSTATES; KEGGIN-TYPE POLYOXOTUNGSTATES; LIQUID-PHASE OXIDATION; HYDROGEN-PEROXIDE; MOLECULAR-OXYGEN; MESOPOROUS SILICA; STRUCTURAL-CHARACTERIZATION; SELECTIVE EPOXIDATION; PORPHYRIN COMPLEXES; AEROBIC EPOXIDATION
categoria
Chemistry
autores
Balula, SS; Cunha-Silva, L; Santos, ICMS; Estrada, AC; Fernandes, AC; Cavaleiro, JAS; Pires, J; Freire, C; Cavaleiro, AMV
nossos autores
Ana Cristina Estrada
Investigador Júnior
Ana Maria Vieira Silva Viana Cavaleiro
Professor Catedrático
Isabel Cristina Maia da Silva Santos Vieira
Investigador Júnioragradecimentos
The authors acknowledge the Fundacao para a Ciencia e a Tecnologia (FCT, MEC, Portugal) for general funding (PEst-C/EQB/LA0006/2011 for Associated Laboratory REQUIMTE and PEst-C/QUI/UI0062/2011 for QOPNA) and Pest-OE/QUI/UI0612/2011 (CQB) and grant SFRH/BD/72058/2010(ACF).