Thermodiffusion in binary and ternary hydrocarbon mixtures studied using a modified heat exchange algorithm

In this paper, a recently proposed modified form of the heat exchange (mHEX) algorithm has been employed to conduct molecular dynamics (MD) simulations of thermodiffusion in binary and ternary hydrocarbon mixtures. Two normal alkane binary mixtures of hexane (nC6)-decane (nC10) and nC6-dodecane (nC12) with varying concentrations of nC12 were studied. In addition to this, the mHEX algorithm was also validated with respect to ternary mixtures: three different compositions of methane (nC1)- butane (nC4)-nC12, and one composition of 1,2,3,4-tetrahydronaphthalene (THN)-nC12-isobutylbenzene (IBB). For the binary mixtures studied here, our findings were in a good agreement with previous work in the literature, i.e., the components in the mixture show less tendency to segregate as the concentration of heavy component in the mixture increases. Additionally, in agreement with the literature, the heavier component separates to the cold side whereas the lighter component separates to the hot side. In ternary mixtures, the mHEX algorithm performs much better than the regular heat exchange algorithm (HEX) in predicting the direction and magnitude of the thermodiffusive separation. Once again, the heaviest and the lightest components clearly separate to the cold and hot side, respectively. With respect to the ternary mixtures, the mHEX algorithm is about 17% more accurate in predicting the thermodiffusive separation than the regular HEX algorithm.