Assessment of activity coefficient models for predicting solid-liquid equilibria of asymmetric binary alkane systems

Hydrocarbon fluids play an important role in today's society, being essential components of oil and fuels. Phase equilibria knowledge of such mixtures is important in designing equipment and processes. Among the least studied equilibriums is that between solid and liquid phases (SLE) which is required in, e.g., wax formation studies. Still, a number of models have been proposed for estimating the activity coefficient but are rarely investigated against SLE data. In this study, a number of 'well-established' and 'up-to- date sophisticated' activity coefficient models are tested for their capability in predicting solid-liquid equilibria of alkane systems. A large database covering 63 alkane/alkane systems for which SLE data are available is considered. The models include several of the popular approaches proposed during the past 30 years covering the gap of a comprehensive literature review. The capabilities and limitations of the models are discussed and those that provide successful predictions are recommended at various levels of accuracy and complexity. Hydrocarbon fluids play an important role in today's society, being essential components of oil and fuels. Phase equilibria knowledge of such mixtures is important in designing equipment and processes. Among the least studied equilibriums is that between solid and liquid phases (SLE) which is required in, e.g., wax formation studies. Still, a number of models have been proposed for estimating the activity coefficient but are rarely investigated against SLE data. In this study, a number of `well-established' and `up-to-date sophisticated' activity coefficient models are tested for their capability in predicting solid-liquid equilibria of alkane systems. A large database covering 63 alkane/alkane systems for which SLE data are available is considered. The models include several of the popular approaches proposed during the past 30 years covering the gap of a comprehensive literature review. The capabilities and limitations of the models are discussed and those that provide successful predictions are recommended at various levels of accuracy and complexity

Surface tension modelling with a combination of the gradient theory with the CPA equation of state

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Modeling vapor-liquid interfaces with the gradient theory in combination with the CPA equation of state

International audienceWith the final purpose of describing the important aqueous + hydrocarbon liquid-liquid interfaces, the gradient theory was combined with the Cubic-Plus-Association equation of state (CPA EOS), taking advantage of the correct representation of interfacial tensions provided by the gradient theory and the correct phase equilibrium of water + hydrocarbon systems already obtained from CPA. In this work, preliminary studies involving the vapor-liquid interfacial tensions of some selected associating and non-associating pure components (water, ethanol, n-butane, n-pentane, n-hexane, n-heptane) are presented and discussed. The good description of equilibrium properties such as vapor pressure and liquid and vapor phase densities is shown in the full range of the vapor-liquid saturation line. For non-associating components, results are compared with those from the Soave-Redlich-Kwong and Peng-Robinson equations of state. A correlation for the influence parameter is presented from which surface tensions can be obtained in a broad temperature range with average errors smaller than 1%

Surface tension modelling with a combination of the gradient theory with the CPA equation of state

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Interfacial tension measurement and modeling of hydrocarbon + water systems

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