Karine Ballerat-Busserolles

Dissociation Constants of Protonated Amines in Water at Temperatures from 293.15 K to 343.15 K

The dissociation constants of protonated 2-amino-1-ethanol (MEA), diethanol amine (DEA), triethanol amine (TEA), methyldiethanol amine (MDEA), 2-amino-2-methyl-1-propanol (AMP), 3-dimethylamino-1-propanol (DMAP), tris(hydromethyl)aminomethane (THAM), 2-[2-(dimethylamino)ethoxy]ethanol (DMAEOE) and, 1,2-bis(2-aminoethoxy)ethane (DiAEOE) were determined in the temperature range 293.15 to 343.15 K using a potentiometric titration method. The experimental technique was first validated using as reference the available literature data of MDEA. The dissociation enthalpies of amines were derived from their dissociation constants using the Van’t Hoff equation. Experimental dissociation constants and dissociation enthalpies were discussed in term of amine structure and compared with literature values when available.

Polymer–surfactant interactions: Thermodynamics of some polypropylene glycols in sodium dodecylsulfate aqueous solutions at 298.15 K. Comparison with cationic CTAB aqueous solutions

Interactions between poly(propylene) glycols and sodium dodecylsulfate, in aqueous solutions were investigated through thermodynamic analysis. Densities and heat capacities, measured with the corresponding well-known Picker apparatus, were determined as a function of the surfactant concentration at 298.15 K. The apparent and transfer molar volumes and heat capacities of the solutes, surfactant and polymer, were deduced therefrom. From the analysis of their variations as a function of the surfactant concentration, it was shown that mainly strong hydrophobic interactions are involved between solutes, similar to the medium chain (C4–C6) 1-alcohols in equivalent surfactant systems. However, the large variations of these properties observed close to the critical micellar concentration signify profound structural changes in micelles caused by the presence of the polymer. Comparison with hexadecyltrimethyl ammonium bromide solutions shows a similar pattern of aggregation and complex formation although the strength and nature of the interactions are somewhat different.

Impact of water on the melting temperature of urea + choline chloride deep eutectic solvent

Deep eutectic mixtures are considered as promising green, cheap and easy-to-prepare solvents for applications in catalysis, extraction or material design. In the present work we focus on the urea:choline chloride system. Our aim was to establish its phase diagram and to quantify the impact of naturally present water on the melting temperature for this highly hygroscopic system. The phase diagram of dried urea:choline chloride was established using three complementary apparatuses: a thermostated bath, an optical microscope and a differential scanning calorimeter. Due to limited thermal stability, only mixtures with urea mole fractions between 0.50 and 0.80 were studied. The eutectic point was found for a urea mole fraction of 0.67 at 25 °C and its enthalpy of melting is 93 J g−1. Water can be easily absorbed from the atmosphere, which decreases the melting temperature of eutectic compositions below room temperature. This is quantified in this paper by a systematic study of the melting temperature of a eutectic mixture containing different quantities of water up to 10 wt%. The presence of water should be taken into account for any physico-chemical characterization as well as for applications of this type of eutectic system.

Molecular Simulations of Primary Alkanolamines Using an Extendable Force Field

A classical force field is proposed for the molecular simulation of primary alkanolamines containing a NH(2)-C-C-OH backbone. A method is devised to take into account the polar (H-bonding) environment of the alkanolamines by calculating electrostatic charges in the presence of explicit solvent molecules. The force field does not use a universal set of charges, but is rather constructed by following a general method for obtaining specific charges for the different alkanolamines. The model is parameterized on the two simplest primary alkanolamines and then validated by calculating thermodynamic properties of five other molecules. Experimental liquid densities and enthalpies of vaporization are also reported in order to complete existing literature data. The predicted ability of the force field is evaluated by comparing the simulation results with experimental densities and enthalpies of vaporization. Densities are predicted with an uncertainty of 1.5 % and enthalpies of vaporization with an uncertainty of 1 kJ mol(-1). A decomposition of the interaction energy into electrostatic and repulsive-dispersive interactions and an analysis of hydrogen-bond statistics lead to a complex picture. Some terms of these interactions are related to the molecular structure in a clear way, others are not. The results provide insights into the structure-property relations that contribute to a better description of the thermodynamic properties of alkanolamines.

Protonation of alkanolamines and cyclic amines in water at temperatures from 293.15 to 373.15 K

Abstract The protonation properties of amines are of particular interest for the development of thermodynamic models representative of CO2 dissolution in aqueous solutions. This paper reports experimental equilibrium constants of protonation of alkanolamines (2-aminoethanol, 2,2′-iminodiethanol, 2-[bis(2-hydroxyethyl)amino]ethanol, 2-amino-2-methylpropan-1-ol, 2,2′-(methylimino)diethanol and cyclic amines (morpholine, 4-methylmorpholine, pyridine, 1-methyl-piperidine, 2-methyl-piperidine, 2,6-dimethylpiperidine). The equilibrium constants of protonation were determined by potentiometric technique up to 353.15 K and extrapolated up to 373.15 K using experimental enthalpies of protonation.

Thermodynamic Properties of CTAB in Aqueous Solutions of Neutral Polymers at 25°C

Interactions of polyethylene glycols (PEGs) and polypropylene glycols (PPOs) in aqueous solutions of hexadecyltrimethylammonium bromide (CTAB) were investigated through thermodynamic properties at 25°C. The densities and heat capacities of the solutions were measured with a vibrating tube densimeter and a Picker flow microcalorimeter, respectively. The variations in the apparent molar volumes and heat capacities of both solutes, calculated from the densities and heat capacities of the solutions, are unusually large in the vicinity of the CMC, reflecting the existence of very strong interactions between CTAB and PPOs. With the more hydrophilic polymers, PEGs, the apparent properties of CTAB are less affected by the presence of the polymer, indicating that PEGs interact only weakly with CTAB.

Thermal analysis of aqueous micellar solutions

A micro differential temperature scanning calorimeter was used to characterize the structural changes between different types of micelles in aqueous solutions of ionic surfactants: anionic — sodium dodecylsulfate (SDS) — and cationic — hexadecyltrimethyl ammonium bromide (CTAB). Moreover, this technique allowed to confirm the existence of peculiar types of complexes between surfactants and selected solutes. In SDS solutions containing polyethylene glycols (PEG), the presence of complexes formed by small micelles adsorbed along the chains of the polymers was evidenced in the case of long enough polymer chains. In CTAB-phenol solutions, due to strong interactions between the polar heads of surfactant and phenol, molecular complexes of a composition of 1:1 molar ratio have been characterized. Depending on the ratio [phenol]/[CTAB], the rheological behaviour was found to change from fluid to viscoelastic and gel-like solutions, owing to the growth of elongated rod-like micelles. With entangled worm-like micelles, the important role of kinetics to reach the thermodynamic equilibria was shown.

Interactions of Alkanolamines with Water: Excess Enthalpies and Hydrogen Bonding.

We report a transferable force field to describe the interactions of alkanolamines based on the N-C-C-O backbone with water, derived from a comparison with experimental excess enthalpies. This force field is tested on 2-aminoethan-1-ol (MEA), 2-amino-2-methylpropan-1-ol, 2-aminobutan-1-ol (ABU), and 1-aminopropan-2-ol. These alkanolamines are derivatives of MEA obtained by substitution with methyl and ethyl groups on the carbon atoms of the N-C-C-O backbone. A specific cross interaction site corresponding to the hydrogen bond between the hydroxyl group of the alkanolamine and the oxygen atom of water was introduced in order to reproduce quantitatively experimental excess enthalpies. The transferability of this specific site was assessed by predictions on alkanolamines that were not included in the parametrization data set. New data on enthalpy of mixing for ABU with water are reported, since they were not available in the literature. From the molecular simulations, several microscopic quantities of the alkanolamine-water mixtures were analyzed in order to improve our understanding of these systems. The structure of the solvation shells at varying compositions, statistics of hydrogen bonds, conformations, and energy decompositions served as bases for an interpretation of the molecular reasons underlying the behavior of the excess enthalpy. The prominent result is that water-water interactions play a major role in differentiating alkanolamine-water mixtures, which is a manifestation of the hydrophobic effect. Both the structural and energetic effects observed at the molecular level point to phenomena that have strong composition dependence, in particular, the interplay between the intramolecular hydrogen bond in the alkanolamine and the intermolecular hydrogen bonds with water.

\mathrm{{CO}}_{2} Capture in Industrial Effluents. Calorimetric Studies

In order to reduce environmental impact of \(\mathrm{{CO}}_{2}\) emissions, one possible option is the decarbonation of the effluents coming from fixed sources. A description of the different techniques proposed for a separation of \(\mathrm{{CO}}_{2}\) from gaseous effluents is explained with a focus on post-combustion processes. The design of specific separation units will require studies of gas dissolution in various selective absorbent solutions. The thermodynamic approach for \(\mathrm{{CO}}_{2}\) dissolution in aqueous solutions of amine is depicted, showing the physicochemical background and the main properties required in this domain. An overview of the main experimental developments for determining the enthalpy of solution of carbon dioxide in absorbent solutions is presented together with some representative results.