A Parametric Study of Dipolar Chain Theory with Applications to Ketone Mixtures

Abstract

Dipolar interactions, which traditionally have been very difficult to model or predict accurately, have a significant effect on the phase behavior of a plethora of systems of industrial importance such as mixtures containing ketones, aldehydes, ethers, and esters as well as polar polymers, copolymers, and a variety of biochemicals. Jog and Chapman proposed a model that accurately predicts the properties of chainlike molecules with single or multiple dipolar sites (Jog, P. K.; Chapman, W. G. Mol. Phys. 1999, 97, 307). In a more recent paper (Jog, P. K.; Sauer, S. G.; Blaesing, J.; Chapman, W. G. Ind. Eng. Chem. Res. 2001, 40, 4641), this theory was extended to mixtures of polar fluids. We continue the analysis and application of the method here in a parametric study using ketones and further demonstrate the ability of the model to accurately predict phase behavior for polar mixtures by applying the method to mixtures of alkanes and ketones of varying lengths. The ketone parameters are very well behaved in that they are smooth functions of molecular weight. The model is able to capture the physics of the phase behavior of a variety of alkane and ketone mixtures, including those of a diketone and alkane mixture. We utilize both the perturbed-chain and Chen−Krewlewski approaches to the dispersion term for the SAFT model, which demonstrates the inclusiveness of the polar term independent of the dispersion term. A comparison with UNIFAC shows the advantage of our polar chain theory for modeling systems containing molecules with multiple dipolar groups.