Sophie Thiebaud-Roux

On-line monitoring of the transesterification reaction between triglycerides and ethanol using near infrared spectroscopy combined with gas chromatography.

Many analytical procedures have been developed to determine the composition of reaction mixtures during transesterification of vegetable oils with alcohols. However, despite their accuracy, these methods are time consuming and cannot be easily used for on-line monitoring. In this work, a fast analytical method was developed to on-line monitor the transesterification reaction of high oleic sunflower oil with ethanol using Near InfraRed spectroscopy and a multivariate approach. The reactions were monitored through sequential scans of the reaction medium with a probe in a one-liter batch reactor without collecting and preparing samples. To calibrate the NIR analytical method, gas chromatography-flame ionization detection was used as a reference method. The method was validated by studying the kinetics of the EtONa-catalyzed transesterification reaction. Activation energy (51.0 kJ/mol) was also determined by considering a pseudo second order kinetics model.

Glycerol acetals and ketals as bio-based solvents: positioning in Hansen and COSMO-RS spaces, volatility and stability towards hydrolysis and autoxidation

Four recently launched cyclic glycerol acetals or ketals are evaluated as bio-based solvents. Three of them are industrially available and result from the condensation of glycerol with formaldehyde, acetone and isobutyl methyl ketone. The fourth is under development and is prepared by the reaction of glycerol with benzaldehyde under heterogeneous acidic catalysis. Their solvent properties are evaluated through Hansen and COSMO-RS (COnductor-like Screening MOdel for Real Solvents) approaches, in comparison with traditional petrochemical solvents. Dioxolane- and dioxane-type isomers have close solubility parameters; however the nature of the starting aldehyde/ketone significantly impacts the solvency properties. The stability to hydrolysis depends heavily on both the aldehyde/ketone part and on the size of the ring. In acidic medium, acetals are found to be more stable than ketals and glycerol-based ketals are more stable than ethylene glycol-based ketals. In the case of benzaldehyde glycerol acetal, it is shown that the 6-membered ring isomer (dioxane-type) is approximately 8 times more stable than the 5-membered ring counterpart (dioxolane-type) at low pH. Stability towards autoxidation by O2 is high for formaldehyde and acetone-derived acetals and drops for the other two compounds. Glycerol acetals and ketals are promising potential alternatives to some harmful solvents such as glycol ethers and aniline.

Synthesis of new cellulose ethers using Suzuki-Miyaura reactions.

Cellulose ethers are functionalized biopolymers that are industrially produced through drastic conditions employing gaseous reactants with a high risk of industrial accident. The cellulose ethers that are commercially available generally bear short carbon-chains. In this work, an alternative method using non-gaseous chemicals is proposed. It relies on the use of the Suzuki-Miyaura reaction employing mild, moisture- and air-stable conditions. Relatively innocuous reagents are used for this step, which allows the formation of a wide range of cellulose ethers bearing various functional groups with different chain-length.

LCA case study: comparison between independent and coproduction pathways for the production of ethyl and n-butyl acetates

PurposeThe production of ethyl acetate and n-butyl acetate was investigated through two different pathways: either by independent reactions or by coproduction. In the coproduction pathway, the n-butyl acetate was produced by reusing the by-products of the synthesis of ethyl acetate. This study provides a comparison of the environmental impacts of these two pathways using a life cycle assessment (LCA). A discussion about the use of LCA on chemicals and its challenges was also developed.MethodsEthyl acetate and n-butyl acetate were synthesized with maximum respect to the principles of green chemistry (use of heterogeneous catalyst, energy savings, minimum steps). An innovative pathway was developed to avoid waste production, by reusing all the by-products of syntheses. After characterizing the feasibility of using these solvents in paint formulations, their potential impacts on the environment were evaluated through a cradle to gate analysis, up to the synthesis at laboratory scale. Most of the foreground data were directly collected with experimental trials. The background data that were not available in the Ecoinvent 3.1 database were estimated thanks to literature or proxys. Evaluations were then performed on the SimaPro 8.1.1 LCA software, using a derivative of ILCD 2011 1.05 as life cycle impact assessment methodology.Results and discussionThe coproduction of both acetates led to the synthesis of purified ethyl acetate (purity of 92.1% w/w) and n-butyl acetate (purity of 97.1% w/w), after distillation. These results were quite similar to those obtained when independent syntheses were carried out. On an environmental point of view, it was found that the reagents preparation was always the step of the process responsible of the majority of the environmental impacts. The comparison between independent syntheses and coproduction showed that recycling the acetic acid produced during the first esterification (ethyl acetate from ethanol and acetic anhydride) led to a decrease of the impacts from 5 to 23% for all the impact categories.ConclusionsThis innovative coproduction of ethyl and n-butyl acetates led to interesting results from both a technical and environmental perspective, with a clear reduction of the environmental impacts. In a context of sustainable chemistry, this appears to be a very interesting way of production. Concerning the LCA of chemicals, a lot of work is still needed in order to improve the accuracy and the reliability of the assessment.