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The Ninth Industrial Fluid Properties Simulation Challenge aimed to test the ability of molecular modeling approaches to predict water/oil interfacial tension (IFT) at conditions of high temperature and pressure. In particular, the challenge featured water/oil IFT where the oil was n-dodecane, toluene, or a 50:50 n-dodecane/toluene blend at 1.825 MPa and temperatures in the range of 383 K to 443 K. Seven entries were received including approaches such as molecular dynamics (MD) and Monte Carlo (MC) simulations, COSMO-RS, and iSAFT, and they were judged by comparison to pendant drop tensiometer benchmark data. The quality of predictions varied among the entries between approximately 20 % and 70 % of the total points possible with the entries based on MD and MC having the highest scores in most cases. As is often the case in molecular modeling, predictions of the relative trends tended to be reliable even if the absolute values were not.

The octanol–water partition coefficients (Ko/w) and infinite-dilution activity coefficients (γ∞) of 1-ethylpropylamine and 3-methyl-1-pentanol were predicted based on free energy calculations. The multi-configuration thermodynamic integration (TI) method was applied with molecular dynamics simulations to calculate free energy changes. With optimized simulation options and force field parameters the calculated free energy changes were highly precise (uncertainties

The primary goal of the fifth industrial fluid properties simulation challenge was to test the ability of computer modeling (any advanced molecular simulation method) to predict the 1-octanol–water partition coefficient, KOW, and infinite-dilution activity coefficient (γ∞) in water. Prediction of 1-octanol–water partition coefficients (which has been widely studied by non-molecular simulation computational methods) is viewed as a stepping stone to a more difficult liquid–liquid (LLE) problem, for example, where a third component is present at a high enough level to influence the mutual solubilities of the other two. To address this primary goal, entrants were challenged to predict KOW and γ∞ for two molecules for which, at the time of the contest, no measured data could be found in phase equilibria databases or literature. The molecules are 1-ethylpropylamine (CAS# 616-24-0) and 3-methyl-1-pentanol (CAS# 589-35-5). All four benchmark values were derived directly from experimental data measured for the simulation challenge at The Dow Chemical Company, Research and Development Department, Analytical Sciences.