Valérie Molinier

Panorama of sustainable solvents using the COSMO-RS approach

Recent regulations have banned numerous common organic solvents that have been recognized as hazardous to human health and environment. There is thus a pressing need for alternatives, often called “green” or “sustainable” solvents, which have a good HSE (Health Safety Environment) profile and are preferably obtained from the biomass feedstock. A number of such green solvents are already on the market or under advanced development and have been listed in this work. To use this set of solvents as effective alternatives, a tool is needed to compare their physico–chemical properties to the ones of the solvents they are supposed to replace. The COnductor-like Screening MOdel for Real Solvents (COSMO-RS) approach was used to model the solvents, which were located in a pseudo 3D-space thanks to Principal Components Analysis and clustering procedures. This approach had already been successfully applied to the classification of classical organic solvents into ten families in which the green solvents have been positioned. This pseudo 3D-representation of green solvents helps in the search of potential alternatives to a questionable solvent. It also sheds light on paucity or even a complete lack of green solvents in some families (e.g. strong electron pair donor bases). There is thus a need to develop new green solvents with the prerequisite properties. As the COSMO-RS approach can be applied to almost any potential candidate, it could be a powerful tool for the design in silico of new sustainable solvents.

Synthesis and foaming properties of new anionic surfactants based on a renewable building block: sodium dodecyl isosorbide sulfates.

Two agro-based anionic surfactants containing an isosorbide moiety have been synthesized and their amphiphilic properties evaluated. Since isosorbide is now considered as an important platform chemical of the starch industry, these compounds could represent bio-sourced alternatives to the alkyl ether sulfates (notably lauryl ether sulfate, LES) that are based on petroleum-derived ethylene oxides. As isosorbide is an asymmetric diol, two isomers can be prepared (2-O-dodecyl isosorbide sulfate and 5-O-dodecyl isosorbide sulfate) that show significantly different aqueous properties as regards to their Krafft temperatures and critical micellar concentrations. 5-O-dodecyl isosorbide sulfate is the most soluble and the most efficient surfactant. It possesses a much lower critical micelle concentration (cmc) than sodium dodecyl sulfate, SDS, leading to comparable foaming properties with a three times lower concentration. Its behavior compares well with the one of pure diethoxylated dodecyl sulfate that has also been prepared and evaluated in this work.

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.

In silico design of bio-based commodity chemicals: application to itaconic acid based solvents

Global issues are deeply changing the face of the chemical industry. Both the feedstock – biomass vs. oil – and the chemical transformations used are now chosen to comply with a sustainable development. In this work, a computer-assisted organic synthesis program, named GRASS (GeneratoR of Agro-based Sustainable Solvents), is proposed to help in the design of sustainable solvents from biomass feedstock. A careful selection of industrially relevant chemical transformations has been performed to propose a set that allows obtaining in a few steps (1 to 3) a large number of commodity chemicals from a chosen set of bio-based building-blocks. Emphasis has been put on solvents since this type of compound is undergoing a deep renewal due to more stringent regulatory constraints, but the same approach may be extended to other commodity chemicals. This methodology has been exemplified starting from itaconic acid, a multifunctional bio-based building block. We checked a posteriori that all itaconic acid based-solvents reported in the literature do indeed belong to the set of virtual solvents generated by GRASS, along with an extended list of new derivatives that could be of potential interest.

Bidimensional analysis of the phase behavior of a well-defined surfactant (C10E4)/oil (n-octane)/water-temperature system.

The equilibrium phase behavior of the well-defined system tetraethyleneglycol decyl ether (C(10)E(4))/n-octane/water (SOW) at variable temperature (T) was revisited by careful analysis of the three bidimensional cuts, namely, the gamma (at constant water-oil ratio), chi (at constant surfactant concentration), and Delta (at constant temperature) plots. A straightforward methodology is reported to determine the frontiers of the triphasic (Winsor III) domain on any cut of the SOW-T phase prism. It comes from the systematic analysis of another cut, here gamma at different water-oil ratios and chi at different surfactant concentrations from the knowledge of Delta cuts at different temperatures. The method has been validated through comparison with experimental results. It enables one to show, for the first time, the evolution of a SOW system three-phase body contours with (i) water-oil ratio, (ii) surfactant concentration, and (iii) temperature. It exhibits a strong impact of the surfactant affinity for the pure oil and water phases on the shape of the phase diagrams. The systematic study of the effect of the surfactant concentration on the aspect of the chi plot sheds light on an unusual shape found at low surfactant concentration.

Telomerisation of 1,3‐Butadiene with 1,4:3,6‐Dianhydrohexitols: An Atom‐Economic and Selective Synthesis of Amphiphilic Monoethers from Agro‐Based Diols

The telomerisation of 1,3-butadiene with a Pd/TPPTS catalytic system in water or an organic solvent was used for the synthesis of C8 ethers from isosorbide, an agro-based diol. The use of water/oil biphasic reaction conditions allowed the selective synthesis of monoethers with improved rates upon using inorganic bases as promotors. As isosorbide is a non-symmetric diol, the two hydroxyl groups display different reactivities. 2-O-substituted-monoethers were preferentially obtained if water was used as the solvent, whereas in DMSO 5-O-substituted monoethers were the major products. Complete conversions of isosorbide with up to 94% monoether selectivities were obtained. The optimized reaction conditions were successfully applied to isomannide and isoidide for the selective synthesis of the derived ethers. An improved reactivity of the endo-hydroxy groups of isosorbide and isomannide versus the exo-hydroxy groups of isosorbide and isoidide was observed if the reaction was performed in DMSO instead of water.

Preparation of amphiphilic sorbitan monoethers through hydrogenolysis of sorbitan acetals and evaluation as bio-based surfactants

Amphiphilic sorbitan acetals have been prepared from sorbitan by acetalisation using linear aliphatic aldehydes or by transacetalisation starting from the corresponding aldehyde diethylacetals. A series of sorbitan acetals has been obtained with 29–81% isolated yields. It has been shown that these sorbitan acetals exist as a mixture of five-membered and six-membered regioisomers. Hydrogenolysis of the mixtures gave the corresponding sorbitan ethers as a mixture of 3 regioisomers with 55–85% isolated yields. A one-pot two-step procedure was also optimized from sorbitan giving similar results. The amphiphilic properties of sorbitan acetals and ethers were evaluated and both families exhibit interesting surfactant properties.

Structure-interfacial properties relationship and quantification of the amphiphilicity of well-defined ionic and non-ionic surfactants using the PIT-slope method.

The Phase Inversion Temperature of a reference C10E4/n-Octane/Water system exhibits a quasi-linear variation versus the mole fraction of a second surfactant S2 added in the mixture. This variation was recently proposed as a classification tool to quantify the Hydrophilic-Lipophilic Balance (HLB) of commercial surfactants. The feasibility of the so-called PIT-slope method for a wide range of well-defined non-ionic and ionic surfactants is investigated. The comparison of various surfactants having the same dodecyl chain tail allows to rank the polar head hydrophilicity as: SO3Na⩾SO4Na⩾NMe3Br>E2SO3Na≈CO2Na⩾E1SO3Na⩾PhSO3Na>Isosorbide(exo)SO4Na≫IsosorbideendoSO4Na≫E8⩾NMe2O>E7>E6⩾Glucosyl>E5⩾Diglyceryl⩾E4>E3>E2≈Isosorbide(exo)>Glyceryl>Isosorbide(endo). The influence on the surfactant HLB of other structural parameters, i.e. hydrophobic chain length, unsaturation, replacement of Na(+) by K(+) counterion, and isomerism is also investigated. Finally, the method is successfully used to predict the optimal formulation of a new bio-based surfactant, 1-O-dodecyldiglycerol, when performing an oil scan at 25 °C.

A “top-down” in silico approach for designing ad hoc bio-based solvents: application to glycerol-derived solvents of nitrocellulose

Potentially effective glycerol-based solvents for nitrocellulose have been designed using a top-down in silico procedure that combines Computer Assisted Organic Synthesis (CAOS) and Molecular Design (CAMD). Starting from a bio-based building block – glycerol – a large number of synthetically feasible chemical structures have been designed using the GRASS (GeneratoR of Agro-based Sustainable Solvents) program. GRASS applies well-selected industrial chemical transformations to glycerol together with a limited number of relevant co-reactants. Then, the most promising structures are considered as lead compounds for further modification in silico thanks to the IBSS (InBioSynSolv) program, which generates derivatives with alkyl, cycloalkyl, alkene, cycloalkene or phenyl substituents. Finally, IBSS ranks all the candidates according to the value of their overall performance function to best fit the predefined specifications, i.e. (i) high solubilisation of nitrocellulose, (ii) slow evaporation and non-flammability (iii) low toxicity and environmental impact. This general strategy enables the highlighting of the most relevant solvent candidate derived from any building block for a given application. To validate the approach, 15 commercially available solvents derived from glycerol were confronted with nitrocellulose and led to highlight diacetin as an effective and safe solvent.

Volatile short-chain amphiphiles derived from isosorbide: Hydrotropic properties of esters vs. ethers

Two series of short-chain isosorbide monoalkanoates, differing from the free hydroxyl position, were synthesized and evaluated as volatile non-ionic hydrotropes, also known as “solvo-surfactants”. Their aqueous solubilities, solubilizing efficiencies and volatilities were evaluated and compared to the corresponding 5-O-alkylisosorbides. Whatever the acylation position (5-O- or 2-O-), isosorbide monoalkanoates are poorly water-soluble for acyl chains longer than four carbons, whereas 5-O-alkylisosorbides are completely miscible with water up to a pentyl chain, which seems to indicate that an ether link brings more hydrophilicity than an ester bond for these types of molecules. The shorter isosorbide monoalkanoates are completely miscible with water and the butanoates are particularly efficient in terms of aqueous solubilization of hydrophobic compounds. In addition, all hydrotropes exhibit some volatility albeit being non-VOC and contrarily to their ethers homologues, isosorbide alkanoates are easily hydrolysed in basic medium, which suggests a good biodegradability.