Mutual Solubility of Water and Hydrocarbons: A New Mixing Rule and the Development of a Predictive Scheme via the Cubic Two-State Equation of State

Abstract

The cubic two-state equation of state was employed for the correlation of measured mutual solubilities of water and 68 hydrocarbons. A new Kabadi−Danner's type mixing rule is presented, in which the water−water dispersive parameter of the cubic part is corrected due to the presence of a hydrophobic solute. The obtained binary parameters for the water−hydrocarbon pairs had a marked relationship with the chemical family (alkanes, cycloalkanes, aromatics, and unsaturated aliphatics) and with the co-volumes. This allowed the development of general correlations to predict these parameters in the case of lack of experimental solubilities. The model's overall deviations from measured data were 12% and 16% for the solubilities of water in hydrocarbons and of hydrocarbons in water, respectively. The temperature and pressure ranges of the correlated data were 273.2 to 550 K and 1 to 1000 bar, respectively. To check model reliability, the correlations were successfully extended to predict bubble pressures and dew temperatures of water−hydrocarbon binaries and ternaries and mutual solubilities in multi-hydrocarbon mixtures.

Correlation of water-chlorohydrocarbon mutual solubilities using a modified non-quadratic mixing rule and the Cubic-Two-State equation of state

“…For the mixture dispersive parameter, the rule suggested by Medeiros and Brindis-Flores [10] is used, where, following Kabadi and Danner's proposal [5], a correction function φ(T,x) is introduced to correct the water-water dispersive a11 due the presence of hydrophobic solutes. The rule has the following form:…”

“…where kij is an adjustable binary interaction parameter. The correction function φ(T,x) has the form suggested by Medeiros and Brindis-Flores [10]:…”

“…where ηi and τi are adjustable parameters related to the hydrophobic solute i. The development and testing of this expression can be found in Medeiros and Brindis-Flores' work [10]. It is important to note that, in Eq.…”

“…The main idea is to correct the water-water interaction due to hydrophobic hydration effects caused by the presence of the organic solute. Our group applied the idea of Kabadi and Danner [5] to the Cubic Plus-Association (CPA) [9] and to the Cubic Two-State (CTS) EoS [10]. The proposed model reproduced the observed minimum in HC solubility reliably and presented a marked relationship with the chemical family and structure of HC heavier than butane [10].…”

“…The main objective of this work is to extend the predictive scheme model developed by Medeiros and Brindis-Flores [10] for water-HC mutual solubility determination to cover water-CHC mixtures. We also employed the CTS EoS coupled to a non-quadratic mixing rule, which corrects the dispersive parameter where the water-water interaction is modified due to the presence of hydrophobic solutes.…”