Limonène | EPFL Graph Search

Le limonène, LIM, de formule brute C10H16, est un hydrocarbure terpénique présent dans de nombreuses huiles essentielles à partir desquelles il peut être obtenu par distillation. À température ambiante, c'est un liquide incolore à odeur brillante, fraîche et propre d'orange, caractéristique des agrumes. Le limonène est utilisé comme solvant dans les produits de nettoyage, la fabrication de produits alimentaires, la parfumerie et les produits d'hygiène, ainsi que comme insecticide. Le limonène tire son nom du citron qui, comme les autres agrumes, contient des quantités considérables de ce composé chimique, responsable en grande partie de leur parfum. Le limonène est une molécule chirale, et, comme pour beaucoup de molécules chirales, les sources biologiques produisent un énantiomère spécifique. La principale source industrielle, l'orange, contient du d-limonène ((+)-limonène), qui est l'énantiomère R dextrogyre. L'eucalyptus et la menthe poivrée, quant à eux, contiennent du l-limonène ((–)-limonène), qui est l'énantiomère S lévogyre. Le limonène racémique est connu en tant que « dipentène ». Le limonène peut favoriser la cicatrisation des plaies et l'anabolisme, tout en améliorant le stress, la dépression, l'inflammation, le stress oxydatif, les spasmes et les infections virales. En outre, il présente une variété de propriétés anticancéreuses. Comme l'odeur principale qui constitue les agrumes (famille des Rutaceae), le D-limonène est utilisé dans l'industrie agroalimentaire ainsi que dans l'industrie pharmaceutique pour parfumer les médicaments, notamment les alcaloïdes amers. Il est également utilisé dans les produits nettoyants pour son odeur rafraîchissante orange-citron et son effet dissolvant. Ainsi, le limonène est également de plus en plus utilisé comme solvant, notamment le dégraissage des machines, puisqu'il est produit depuis une source renouvelable, l'huile de citrus, comme un sous-produit de la fabrication de jus d'orange. Le limonène fonctionne comme solvant à peinture lorsqu'elle est appliquée sur du bois.

Design, Synthesis and Characterization of New Nanoparticle Stabilizers and Their Application in Catalysis

Ilaria Biondi

In recent years, a strong emphasis in research towards creating sustainable and environmental friendly chemical processes has propelled the development of novel types of catalytic systems that combine advantages from homogeneous and heterogeneous processes. In this respect, transition metal based nanoparticles, TM-NPs, are excellent candidates with properties that offer high efficiency, high selectivity and the possibility of recycling. However, due to the particularly small size, within the nanoscale, TM-NPs are generally only kinetically stable and must be supported or stabilized by molecular systems to prevent aggregation into larger, less active materials. The work presented herein concerns the design, synthesis, characterisation and the applications of new TM-NP protecting agents, which are based on polymers functionalized with components that compose ionic liquids, P-ILs. Specifically, these P-ILs feature a hydrophobic poly-norbornene framework prepared using Ring Opening Metathesis Polymerization, ROMP, with pendant imidazolium-based ionic liquid substituents that allow fine tuning of the polymer solubility by anion-exchange. In Chapter 2, an aqueous, soluble P-IL containing the 1,2-dimethylimidazolium methane-sulphonate substituent and its use in the synthesis of aqueous gold NP, GNP, solutions is described. These particular TM-NPs were characterized by UV-VIS spectroscopy and Transmission Electron Microscopy, TEM. Subsequently, the P-IL/GNP solutions were used to catalyse the reduction of p-nitrophenol and the hydrogenation of cinnamaldehyde, both reactions are found to exhibit excellent activity under mild conditions. In Chapter 3, the potential of aqueous P-IL stabilizers to transfer GNPs from water to hydrophobic ILs and organic solvents is demonstrated. Using an anion-exchange process, the phase change does not result in GNP aggregation, as confirmed by UV-VIS spectroscopy and TEM analysis. Moreover, the same P-ILs were used as a protecting agents for the synthesis of aqueous rhodium NPs, RhNPs, which have been applied in the catalytic hydrogenation of natural compounds, including limonene, cinnamaldehyde, citral and α- and β-ionones. Through anion-exchange, the aqueous P-IL stabilized RhNPs are readily transferred into hydrophobic ILs, then used as catalysts in the hydrogenation of styrene and limonene. The stabilized RhNPs exhibited good activity, even after recycling. X-ray Photoelectron Spectroscopy, XPS, analysis demonstrated conclusively that the anion exchange and phase transfer of the Rh/Au-NP-IL system. In Chapter 4, three P-ILs containing poly-oxy linker groups, strategically placed between the poly-norbornene framework and the ionic groups, are described. The linkers provide additional stabilization through steric stabilization and coordination via the ether functional groups. These P-ILs were used to stabilize aqueous GNPs, which were characterized by UV-VIS spectroscopy and TEM. Their application in the reduction of p-nitrophenol reduction was demonstrated. Preliminary studies on the stabilization mode of PILs shown that the polymers, despite the presence of ionic groups, can stabilize electrostatically stabilized aqueous GNPs which otherwise aggregate in presence of water soluble imidazolium-based ILs. Moreover, they display good efficiency in terms of steric stabilization, comparable to systems featuring the poly-vinylpyrrolidone, PVP.

EPFL2011

Design, Synthesis and Characterization of New Nanoparticle Stabilizers and Their Application in Catalysis

Ilaria Biondi

EPFL2011