Isomerization of α-pinene oxide catalyzed by iron-modified mesoporous silicates

Abstract

Iron-modified mesoporous silicates (Fe-MCM) were prepared through a direct hydrothermal method and characterized by N2 adsorption–desorption, XRD, Mössbauer spectroscopy and SEM-EDS techniques. The nature of the iron precursor (Fe2+ or Fe3+) strongly affected the textural and morphological properties of the materials. Fe2+-MCM presented the morphology similar to sheets with nanometer dimensions, while Fe3+-MCM was more similar to the non-modified MCM. Characterizations suggest that most of the introduced iron species present on the material surface rather than in the silicate framework. Besides the framework included Fe3+ ions (0.2–0.3wt.%), both materials contain only the trivalent iron (as hematite). Hematite nanoparticles are highly dispersed on the Fe3+-MCM surface, whereas in Fe2+-MCM, hematite forms particles of both low and high dispersion. The materials were shown to be efficient heterogeneous catalysts for the transformation of α-pinene oxide in various value-added fragrance compounds, with the product distribution being remarkably dependent on the solvent nature.