Óxidos ternários nanoestruturados à base de Ce e Fe aplicados à óxidos do etilbenzeno

Abstract

Porous ternary oxides type CeFeMe (Me = Ni, Mn or Co) were obtained by nanocasting using polymeric beads, as a mold. The solids were characterized by scanning electron microscopy coupled to energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), nitrogen adsorption-desorption measurements, Raman spectroscopy and electron paramagnetic resonance (EPR). The solids were evaluated for the production of acetophenone, benzaldehyde and benzoic acid, via the ethylbenzene oxidation with H2O2 in the presence of acetone. SEM analyses suggested that the replication strategy allowed the solids to retain the textural, morphological and structural properties of the mold. XRD mesurements indicated that the structure of CeFeMn, CeFeNi and CeFeCo have low crystallinity and high textural properties due to their nanostructured features. Raman spectra confirmed the existence of phases such as CeO2 (fluorite) e γ-Fe2O3 (spinel) in all solids. Notably, additional phases such as NiO, MnOx and Co3O4 were found in CeFeNi, CeFeMn and CeFeCo, respectively. EPR analysis of the solids revealed that Fe3+/Fe2+ sites were present in the solids. Moreover, the structure of the catalysts was highly dependent on the promotor addition, and the textural properties were related to the structure and morphology of the solids. Thus, CeFe added to Ni produced NiO phase with redox ability to convert about 82% of ethylbenzene into acetophenone, benzaldehyde and benzoic acid, with 30%, 22% e 17% of yield, respectively.