Solubility of water in n-alkanes: New experimental measurements and molecular dynamics simulations

Solubility of water in mixtures of (n-alkanes + n-perfluoroalkanes) and in n-perfluoroalkylalkanes: experiments and modelling with the SAFT-γ Mie group-contribution approach

“…The sampling is performed using a Hamilton gas-tight glass and PTFE syringe, which is kept warmer than the equilibration temperature during the sampling and weighing process to avoid the loss of water by phase separation on cooling. As in the previous studies [29,40], frequent verification of the solubility of water in n-heptane ensures the stability of the measurements and the internal consistency of the obtained data. The careful evaluation of these results is consistent with an intrinsic relative dispersion of the method of up to 5%.…”

“…One would expect that a series of solubility measurements performed in the same laboratory, by the same researchers and using the exact same procedure, has a degree of internal consistence that allows a more detailed analysis. For this reason, we previously performed a series of experimental measurements of the temperature dependence of the solubility of water in four n-alkanes [40] and five n-perfluoroalkylalkanes [29]; furthermore, in our current work we report new solubility measurements of water in n-perfluorohexane and in an equimolar mixture of n-hexane + n-perfluorohexane.…”

“…As discussed in more detail in previous work [40], the experimental determination of the solubility of water in alkanes, and by extension in other essentially nonpolar organic liquids, is prone to a very large uncertainty: discrepancies of more than 100% between authors are not uncommon, and a joint compilation [49] by IUPAC and NIST includes data with deviations of up to 30% between different recommended sources. This intrinsic uncertainty makes the task of performing a detailed interpretation of the solubility very difficult, as the rationalisation of the different contributions to the thermodynamics of the mixtures can easily be lost in the large discrepancies in the values from different sources.…”

“…With this approach, a very good global description of the n-alkane + water fluid-phase behaviour was achieved. In our current work, however, we re-parameterise the unlike interaction between water and the n-alkane (CH 3 and CH 2 ) groups to quantitatively reproduce our recently published experimental solubility data [40] of water in n-hexane, n-heptane, n-undecane, and n-hexadecane over the temperature range of 283-318 K, thus focusing on the organic hydrocarbon-rich phase. Only the unlike interaction energies (ε kl ) are re-parameterized, with all the remaining interaction parameters fixed by the combining rules (equations 4 and 6).…”

“…The solubility of water in n-perfluorohexane and in an equimolar mixture of n-hexane and n-perfluorohexane are determined following the same procedure used in previous work from our laboratory [29,40]. In summary, the equilibration between the aqueous and organic phases is achieved after a minimum of 24 h of direct contact between the phases, inside thermostated glass flasks.…”