22 research outputs found

    [BMIm][BARF] imidazolium salt solutions in alkyl carbonate solvents: Structure and interactions

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    Solutions of weakly coordinating ionic liquids (ILs) in alkyl carbonates are gaining growing attention, as the latter are "green" solvents with high solvation power, but the phase behavior and structure of ILs in organic polar solvents are still poorly understood. Here, we study the interactions and nanoscale structure of 1-butyl-3-methylimidazolium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, [BMIm][BARF], in three symmetrical alkyl carbonate solvents with increasing alkyl chain-length. Electrical conductivity and nuclear magnetic resonance measurements showed that [BMIm][BARF] was mostly undissociated in these solvents, especially at lower IL concentration. Small angle X-ray scattering patterns evidenced the presence of rod-like nanostructures in the IL/solvent mixtures. At higher IL concentration, [BMIm][BARF] is increasingly more dissociated in solvents with lower dielectric constant, as confirmed by analysis of the solvents' carbonyl stretching band via Fourier transform infrared spectroscopy. This trend is opposite to that exhibited by BMIm ILs with less bulky counterions. The bulky BARF(-) is weakly coordinating and has no ability to give strong H-bonding, thus short-range anisotropic van der Waals forces are likely key in the interaction of the ion pairs. The slower self-diffusion of the ions in alkyl carbonates with lower dielectric constants might partially hinder close contact needed for self-assembly into local nano-sized structures. Overall, our results shed light on interactions and self-organization in imidazolium salt-alkyl carbonate mixtures, with potential impact in applicative fields spanning from batteries, catalysis and extraction, up to bio-applications (antimicrobial and bioengineering)

    Unsaturated Renewable Oil Transformation into Novel Biofuel Compositions via an Olefin Metathesis-Transesterification-Hydrogenation Sequence

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    The sequential ethenolysis, transesterification and hydrogenation of a model unsaturated renewable oil for the preparation of potential biofuels is reported herein. Ethenolysis conversions of up to 70%, using olive oil, were obtained applying a relatively low 2 bar ethylene pressure and toluene as solvent. The ethenolyzed olive oil was quantitatively transesterified with methanol and, subsequently, hydrogenated with molecular hydrogen over Pd/C, affording access to novel biofuel compositions, including different fractions of biogasoline, biokerosene and biodiesel.O uso sequencial de rea√ß√Ķes de eten√≥lise, transesterifica√ß√£o e hidrogena√ß√£o de um √≥leo renov√°vel modelo para a prepara√ß√£o de potenciais biocombust√≠veis √© reportado. Convers√Ķes de at√© 70% foram obtidas na eten√≥lise de √≥leo de oliva usando uma press√£o relativamente baixa de etileno (2 bar) e tolueno como solvente. O √≥leo de oliva etenolisado foi transesterificado quantitativamente com metanol e, posteriormente, hidrogenado com hidrog√™nio molecular sobre Pd/C, resultando em novas composi√ß√Ķes de biocombust√≠veis, incluindo diferentes fra√ß√Ķes de biogasolina, bioquerosene e biodiesel

    The synergistic effect of an imidazolium salt and benzotriazole on the protection of bronze surfaces with chitosan-based coatings

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    The class of imidazolium salts contains effective anticorrosion additives for metal substrates. This study evaluated the potential of 1-carboxymethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (HO2CC1MImNTf2) for application in cultural heritage, exploring it as anticorrosion additive in chitosan-based coatings for the protection of copper-based alloys. Under accelerated corrosion conditions with HCl vapor, the chitosan coating with HO2CC1MImNTf2 was less effective than the one with benzotriazole. The coating with a combination of HO2CC1MImNTf2 and benzotriazole resulted in the optimal protective efficacy of the bronze surface, and it also maintained high transparency without changing the bronze appearance.[Figure not available: see fulltext.

    Preparation and electrocatalytic activity of gold nanoparticles immobilized on the surface of 4-mercaptobenzoyl-functionalized multiwalled carbon nanotubes

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    Multiwalled carbon nanotubes (MWCNTs) were functionalized with 4-mercaptobenzoic acid in a polyphosphoric acid/phosphorus pentoxide medium to produce 4-mercaptobenzoyl-functionalized MWCNTs (MB-MWCNTs). Gold nanoparticles (GNPs), stabilized by trisodium citrate, were prepared from the in situ reduction of gold(III) chloride trihydrate by sodium borohydride in the presence of MB-MWCNTs dispersed in ethanol. The morphology of the resulting GNP/MB-MWCNT hybrid showed that GNPs were formed with an average diameter of 4.3 nm, and these were uniformly deposited on the surface of the MB-MWCNTs. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy studies revealed that the GNPs had a well-defined crystal structure. Cyclic voltammetry results showed a high electrocatalytic activity and electrochemical stability of the GNP/MB-MWCNT hybrid in both acidic and basic media.close7

    Interaction Energies of Ionic Liquids with Metallic Nanoparticles: Solvation and Stabilization Effects.

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    International audienceThe interaction energies and solvation structure of ruthenium nanoparticles (RuNPs) in ionic liquids are studied here by titration calorimetry and by molecular simulation. The size of metallic nanoparticles synthesized in situ in ionic liquids can be controlled, and the resulting suspensions are stable without additional surface-active molecules. However, little is known about the energetics and mechanisms of solvation of nanoparticles in these complex, structured solvents. Ionic liquids were added into a suspension of RuNPs in [C1C4Im][NTf2], and the heat effect was recorded. The background heat of mixing of the two ionic liquids was measured separately. The interaction energy of [C1CnIm][NTf2] (n = 6, 8, 10) with RuNPs is larger than that of [C1C4Im][NTf2] indicating that longer alkyl side chains enhance the interactions with RuNPs. [C1C2Im][NTf2] also has stronger interactions with the nanoparticles, but this cation does not possess a significant nonpolar moiety. Ionic liquids with lesser propensity to form Hbonds such as [C1C1C4Im][NTf2] or [C1C4Pyrro][NTf2] interact less favorably with RuNPs. No significant effect of the anion structure was observed when changing the ionic liquid from [C1C4Im][NTf2] to [C1C4Im][PF6]. Structural information from molecular simulation shows that the charged head groups of both the cations and the anions are in contact with the nanoparticle, with only small charge separation at the interface. Alkyl side chains tend to point away from the nanoparticle but are still within interaction range. The overall picture results from a balance between electrostatic, van der Waals, and H-bond forces, which changes between different ionic liquids