resumo
A series of first-row-transition-metal ferrite magnetic nanoparticles (NPs) MFe2O4 [M = Mn2+ (1), Fe2+ (2), Co-2+ (3), Ni2+ (4), Cu2+ (5) or Zn2+ (6)] were prepared by the co-precipitation method and characterized by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscope -energy dispersive X-ray spectrometry (SEM-EDS), vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). Those NPs were used as catalysts for the microwave-assisted oxidation of various alcohols in solvent-free medium. MnFe2O4 (1), CoFe2O4 (3) and CuFe2O4 (5) act as catalysts for the conversion of alcohols to the corresponding ketones or aldehydes with a yield range of 81 to 94% in 2 h at 120 degrees C using t-BuOOH as an oxidant. These catalysts can be readily isolated by using an external magnet and no significant loss of activity is observed when reused up to 10 consecutive runs. The effects of some parameters, such as temperature, time, type of oxidant and presence of organic radicals, on the oxidation reactions were also investigated. The presented literature overview highlights the advantages of our new 1-6 NPs catalytic systems in terms of efficiency and economy, mainly due the used microwave (MW) heating mode.
palavras-chave
ASSISTED PEROXIDATIVE OXIDATION; LIQUID-PHASE OXIDATION; BENZYL ALCOHOL; AEROBIC OXIDATION; SELECTIVE OXIDATION; RECOVERABLE CATALYST; HYDROGEN-PEROXIDE; COFE2O4 NANOPARTICLES; FE3O4 NANOPARTICLES; CARBON NANOSPHERES
categoria
Chemistry
autores
Martins, NMR; Martins, LMDRS; Amorim, CO; Amaral, VS; Pombeiro, AJL
nossos autores
Carlos Amorim
Investigador Auxiliar
Vitor Brás Sequeira Amaral
Professor CatedráticoGrupos
G2 - Materiais Fotónicos, Eletrónicos e Magnéticos
G6 - Materiais Virtuais e Inteligência Artificial
agradecimentos
This work has been supported by the Foundation for Science and Technology (FCT), Portugal (UID/QUI/00100/2013, PTDC/QEQ-ERQ/1648/2014 and PTDC/QEQ-QIN/3967/2014 projects). NMRM express gratitude to FCT for the PhD CATSUS fellowship (SFRH/BD/52371/2013). Work was also supported by project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. The authors thank C.P.M. Sa for the assistance of the XPS analytical services of CEMUP and I. Nogueira for the SEM analysis of MicroLab IST.