Modified interacting-sphere model for self-diffusion and infinite-dilution mutual-diffusivity of n-alkanes

Abstract

The interacting-sphere (IS) model has been modified by introducing a multiple hard-sphere term, N, into the probability function of molecular collisions. The new model was critically evaluated with regards to experimental self-diffusivities covering wide ranges of temperature and pressure. The modification corrects the probability function for multiple hard-spheres and is particularly beneficial for n-alkanes larger than n-triacontane. A generalized version of the modified IS model was presented and required only the carbon number in order to predict n-alkane self-diffusivity. The new model was also used to correlate infinite-dilution mutual-diffusivity by making use of recently published molecular dynamics computer results. A binary interaction parameter, correcting interaction energy between unlike molecules, was introduced and proven independent of temperature for a given molecular pair, but dependent on which component was chosen to be in infinite dilution. The overall standard deviation for infinite-dilution mutual-diffusivity was 3.44%.