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Consistent phase equilibrium data for cyclopentane hydrates in presence of salts are vitally important to many industries, with particular interest to the field of hydrate-based water separation via cyclopentane hydrate crystallization such as desalination. However, there are very little experimental equilibrium data, and no thermodynamic prediction tools. Hence, we set up a method to generate a great deal of much needed equilibrium data for cyclopentane hydrates in diverse saline solutions with a wide range of salt concentrations. Our method does furnish verified, reliable and accurate equilibrium data. Plus, three thermodynamic approaches are developed to predict equilibrium, and provide tools for simulations, by considering the kind of salt and concentrations. All three models are in very good accordance with experimental data. One method, using a new correlation between occupancy factor and water activity, might be the best way to obtain consistent, quick, and accurate dissociation temperatures of cyclopentane hydrate in brine.a Dh b2L w j T 0 ;P 0 5 Dl b2I w j T 0 ;P 0 -6011, where 6011 is the enthalpy of ice (J mol 21 ).

This article presents a systematic review on the past developments of Hydrate-Based Desalination process using Cyclopentane as hydrate guest. This is the first review that covers all required fundamental data, such as multiphase equilibria data, kinetics, morphology, or physical properties of cyclopentane hydrates, in order to develop an effective and sustainable desalination process. Furthermore, this state-of-the-art describes research and commercialization perspectives. When compared to traditional applications, cyclopentane hydrate-based desalination process could be a promising solution. Indeed, it operates under normal atmospheric pressure, lower operation energies are required, etc… However, there are some challenges yet to overcome. A decision aid in the form of a diagram is proposed for a new cyclopentane hydrates-based desalination process. Hopefully, concepts reviewed in this study will suggest new ideas to advance technical solutions in order to make commercial hydrate-based desalination processes a reality.

Mixed Clathrate hydrates are an important issue in many fields, like flow assurance in the oil industry, as well as gas capture and storage, air conditioning, etc… Usually, studies of gas hydrates from hydrocarbon gas mixtures do not mention the volume of hydrate, nor the hydrate composition, and ternary or quaternary mixtures are not considered. Also, data involving propane and butane are limited. Therefore, we suggest both an experimental and modeling study of mixed clathrate hydrates from N 2-CO 2-CH 4-C 2 H 6-C 3 H 8-C 4 H 10 gas mixtures, in temperature range of [0.8-19°C] and pressure range of [1.4-66bars]. The experimental work provides 78 equilibrium points. Two procedures were used to perform crystallizations. The main procedure (71 equilibrium data) corresponds to a method at high crystallization rate (high supersaturation, or high ΔP). The first objective is to study the gas hydrates formation in usual dynamic conditions (start-up or reboot of an oil exploitation). The second method, 7 data, corresponds to a low rate of crystallization. This second objective is to investigate the impact of the speed of crystallization on the final equilibrium. For both procedures, P-T data are given, as well as the compositions of each phase at equilibrium. At last, thermodynamic modeling is used to compare the experimental results of both procedures. Kihara parameters of N 2 , CO 2 and CH 4 are taken from the literature, while parameters for C 2 H 6 are regressed and given in this work. Results show a better agreement of the thermodynamic modeling with experimental study for pure gas hydrate and mixed gas hydrates at low crystallization rate. This observation suggests that mixed gas hydrates might form at thermodynamic equilibrium only at low crystallization rate.

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 9732To link to this article :

The solubility of seven pharmaceutical compounds (paracetamol, benzoic acid, 4-aminobenzoic acid, salicylic acid, ibuprofen, naproxen and temazepam) in pure and mixed solvents as a function of temperature is calculated with SciPharma, a semi-empirical approach based on PC-SAFT, and the NRTL-SAC model. To conduct a fair comparison between the approaches, the parameters of the compounds were regressed against the same solubility data, chosen to account for hydrophilic, polar and hydrophobic interactions. Only these solubility data were used by both models for predicting solubility in other pure and mixed solvents for which experimental data were available for comparison. A total of 386 pure solvent data points were used for the comparison comprising one or more temperatures per solvent. SciPharma is found to be more accurate than NRTL-SAC on the pure solvent data used especially in the description of the temperature dependence. This is due to the appropriate parameterization of the pharmaceuticals and the temperature-dependent description of the activity coefficient in PC-SAFT. The solubility in mixed solvents is predicted satisfactorily with SciPharma. NRTL-SAC tends to overestimate the solubility in aqueous solutions of alcohols or shows invariable solubility with composition in other cases.

International audienceClathrate hydrates, usually called gas hydrates, are compounds of great interest in oil industry, as well as in gas separation and storage, water purification etc… Like many other compounds that phase change, in this case from liquid water to non stochiometric crystalline compound, modeling is required to understand and optimize the processes that involve them.Therefore, the classic thermodynamic equilibrium model is combined with mass balance calculations during gas hydrate crystallization. Two frameworks for performing clathrate hydrate thermodynamic flash calculations at constant volume are presented and compared to experimental results at low crystallization rate. The inputs are the quantity of mass (water and gas molecules), and the volume. The variable is temperature (three phases thermodynamic flash at a given temperature), while the volume is kept constant.The first framework suggests that the hydrate phase is growing at local thermodynamic equilibrium, without any reorganization of its content of the occupancy of the cavities. In the second framework, the hydrate phase can reorganize itself during growth (locally or completely). These frameworks are investigated, as well as the impact of the Kihara parameters uncertainties.These frameworks calculate well the final pressure, hydrate composition. In addition, the hydrate volume and mole amount in each phase is provided with reasonable accuracy. Note: uncertainties on the final pressure and hydrate volume are below 5%. Moreover, the results are quite sensitives to the value of the Kihara parameters, demonstrating the importance of their values for a given computer code.This work provides a more reallistic and comprehensive view of gas hydrate crystallization

Cyclopentane hydrates-based salt removal is considered to be a possible promising technology for desalination. In order to optimize such processes, phase equilibrium data of Cyclopentane Hydrates (CPH) in saline solutions are crucial. Lamentably, these data sets are still incomplete.Therefore, earlier we published a limited experimental and modeling study on CPH equilibrium with some salts present.This study extends experimental equilibrium to four more common brine systems: Na 2 SO 4 , MgCl 2 , MgCl 2 -NaCl, or MgCl 2 -NaCl-KCl at various salt concentrations. Importantly, four thermodynamic approaches: the Standard Freezing Point Depression equation based (SFPD), Hu-Lee-Sum (HLS) correlation, and the two van der Waals and Platteuw-based Kihara and Activity-Based Occupancy Correlation (ABOC) methods, are compared to this new set of experimental data. Results show that simulations agree adequately with measured data. Nonetheless, the ABOC method is the best model to reproduce rapid and consistent equilibrium data of CPH in brine, whatever the electrolytes involved.