Séverine Camy

Glycerol as a cheap, safe and sustainable solvent for the catalytic and regioselective β,β-diarylation of acrylates over palladium nanoparticles

Herein we show that glycerol can be considered as a promising cheap and green solvent for the regioselective β,β-diarylation of alkenes. Whereas this reaction is generally catalyzed under an inert atmosphere by expensive phosphine or carbene-palladium complexes, we show here that the diarylation of alkenes can be conveniently achieved in glycerol in the presence of air-stable palladium nanoparticles. These palladium nanoparticles were stabilized over a sugar-based surfactant derived from biomass. By an adjustment of the reaction temperature, we were able to control the mono- and diarylation step of alkenes, thus offering a convenient route to unsymmetrical diarylated alkenes. At the end of the reaction, the diarylated alkenes were cleanly and selectively extracted from the glycerol-palladium catalytic phase using supercritical carbon dioxide, thus affording a convenient purification work-up. Within the framework of green chemistry, this work combines (i) catalysis in a cheap, safe and sustainable medium, (ii) easily made and air-stable palladium nanoparticles as the catalyst, and (iii) a clean and selective extraction of the reaction products with supercritical carbon dioxide.

Enhancement of Poly(vinyl ester) Solubility in Supercritical CO2 by Partial Fluorination: The Key Role of Polymer–Polymer Interactions

An enhancement of poly(vinyl ester) solubility in supercritical carbon dioxide (sc-CO(2)) can be achieved by decreasing the strength of the polymer-polymer interactions. To demonstrate this, a library of statistical copolymers of vinyl acetate and vinyl trifluoroacetate was synthesized by RAFT/MADIX polymerization with varying compositions at a given number-average molecular weight. These copolymers exhibited unprecedentedly low cloud-point pressures in sc-CO(2) at 40 °C compared with previously reported poly(vinyl esters). Surface tension measurements combined with a computational approach evidenced the prominent role played by polymer-polymer interactions.

Cellulosic materials as biopolymers and supercritical CO2 as a green process: chemistry and applications

In this review, we describe the use of supercritical CO2 (scCO2) in several cellulose applications. The focus is on different technologies that either exist or are expected to emerge in the near future. The applications are wide from the extraction of hazardous wastes to the cleaning and reuse of paper or production of glucose. To put this topic in context, cellulose chemistry and its interactions with scCO2 are described. The aim of this study was to discuss the new emerging technologies and trends concerning cellulosic materials processed in scCO2 such as cellulose drying to obtain aerogels, foams and other microporous materials, impregnation of cellulose, extraction of highly valuable compounds from plants and metallic residues from treated wood. Especially, in the bio-fuel production field, we address the pre-treatment of cellulose in scCO2 to improve fermentation to ethanol by cellulase enzymes. Other reactions of cellulosic materials such as organic inorganic composites fabrication and de-polymerisation have been considered. Cellulose treatment by scCO2 has been discussed as well. Finally, other applications like deacidification of paper and cellulosic membranes fabrication in scCO2 have been reviewed. Examples of the discussed technologies are included as well.

Continuous Production of Biodiesel with Supercritical Methanol: a Simple Compressible Flow Model for Tubular Reactors

From an industrial point of view, the continuous process for biodiesel production with supercritical methanol (SCM) is more appropriate than the batch process. However, lab-scale studies on the continuous process have shown that the maximum conversion always remains slightly lower than that obtained in the batch process. This work proposes a simple compressible flow model to predict the conversion of methanol and oils into methyl esters (ME) along the length of a tubular reactor and further demonstrates the effect of the development of the compressibility factor of the reaction mixture upon the conversion efficiency to ME. The governing equation was derived from a general molar balance in the tubular reactor using transesterification kinetics of refined-bleached-deodorized (RBD) palm oil in SCM coupled with a suitable thermodynamic model with adjusted binary interaction parameters. Vapor-liquid equilibrium data for triolein + methanol, methyl oleate + methanol and glycerol + methanol mixtures were obtained from the literature and then refitted with the thermodynamic model consisting of the Peng-Robinson equation of state and MHV2 mixing rules to find the set of adequate interaction parameters. In order to check the validity of the proposed model, the predicted ME contents were compared with observed values in a lab-scale continuous reactor at various operating temperatures, pressures and methanol to oil molar ratios. The proposed model proved to be adequate for predicting the final conversion to ME for operating temperatures below 320°C, when the thermal degradation reactions of unsaturated fatty acids did not interfere. Our results also illustrate the importance of taking into account the development of the compressibility factor with time and reactor length, since this was shown to be the cause of the lower transesterification reaction rate in the tubular SCM process. The findings in this work could be employed as a knowledgebase to further develop a better model for continuous production of biodiesel with SCM in a tubular reactor.

CO2-Expanded Alkyl Lactates : A Physicochemical and Molecular Modeling Study

With the perspective of finding alternative benign media for various applications, this paper presents a study of the physicochemical behavior of some members of the alkyl lactate family when expanded by CO2. Experimental and molecular modeling techniques have been used to determine and/or predict relevant physicochemical properties of these systems such as swelling, Kamlet–Taft parameters {polarity/polarizability (π*) and proticity or hydrogen-bond donator ability (α), dielectric constants and solubility parameters}. To complete the study of these properties, sigma profiles of the three lactates molecules have been obtained by performing quantum mechanical and phase equilibria calculations of CO2/alkyl lactate systems by using the Peng–Robinson equation of state.

Fatty acid composition, cytotoxicity and anti-inflammatory evaluation of melon (Cucumis melo L. Inodorus) seed oil extracted by supercritical carbon dioxide

ABSTRACT Melon seed oil has been extracted by Soxhlet (hexane) and by supercritical CO2 operating to various pressures and temperatures. Linoleic acid (67.06–68.22%) was the most abundant followed by oleic acid (21.63–22.45%), palmitic acid (5.57–6.23%) and stearic acid (2.98–3.67%). The highest inhibition of inflammation was 18.8% at 50 µg/mL for hexane and SC-CO2 extracts obtained under 55 MPa and 70°C. The largest inhibition of IGROV and OVAR tumor cell lines were 29.9% and 21.6%, respectively, at 50 µg/mL for the ethanol extract. These results of biological activities indicate that melon seed oils can be dedicated to nutrition.