International audienceThe thermodynamic approach developed by Paricaud [J. Phys. Chem. B 2011, 115, 288-299] is applied to predict the dissociation conditions of semiclathrate hydrates made with tetra-n-butyl ammonium bromide (TBAB) tetra-n-butyl ammonium chloride (TBAC), tetra-n-butyl ammonium fluoride (TBAF), and tetra-n-butyl phosphonium bromide (TBPB). The SAFT-VRE equation of state is used to describe the properties of fluid phases, and a good description of osmotic and mean activity coefficients of electrolyte solution is obtained. The temperature-composition diagrams of water + tetra-n-alkylammonium/alkylphosphonium salt binary systems are well described by the model. Group contribution methodsare proposed to predict the fusion enthalpies and the cogruent melting points of semiclathrate hydrates. The van der Waals and Platteeuw theory is combined with the model to calculate the dissociation conditions of carbon dioxide semiclathrate hydrates. The liquid-vapor-hydrate three phase lines can be accurately described over wiede ranges of pressure and salt concentrations, by optimizing only one parameter per hydrate phase

In the context of chemical enhanced oil recovery (EOR), there is no well-established way to characterize and understand the physical properties and structures of microemulsions composed of crude oil and industrial surfactants due to their complexity. Making a comparison to a well-studied model system is a simple and effective way to investigate the complex microemulsions. The purpose of this study is to provide and complete experimental characteristic data of model-microemulsions as a basis of analysis of the complex system. Types of microemulsions studied in the present work were oil in water (O/W), bicontinuous, and water in oil (W/O). The system was composed of water, sodium dodecyl benzenesulfonate (SDBS), isobutanol, sodium chloride (NaCl), and decane. We performed several experiments at room temperature such as spinning drop method, differential scanning calorimetry (DSC), Karl Fischer titration, Hyamine titration, dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and electron cryomicroscopy (cryo-SEM). The measurements provided a deeper insight into a correlation between physical properties and morphologies of water/oil in the microemulsions.

Dissociation conditions of hydrogen semiclathrate hydrates with tetrabutylammonium chloride (TBAC) are measured using a differential scanning calorimeter at the TBAC weight fraction of 0.10, 0.20, 0.35, and 0.50 in the pressure range up to 15.5 MPa. The hydrogen storage capacity of TBAC semiclathrate hydrate is estimated with measured equilibrium data, dissociation enthalpies, and the Clapeyron equation. The amount of hydrogen stored in the semiclathrate hydrate is found to be 0.11 wt % at 15.5 MPa. The model proposed by Paricaud [J. Phys. Chem. B 2011, 115, 288−299] is applied to predict the dissociation condition of the H 2 semiclathrate hydrate with TBAC. The parameters in the model have been determined by describing the liquid−vapor−hydrate three phase lines measured in this work and from the literature. The hydrogen storage capacity predicted by the model is in excellent agreement with the experimental value.

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