Complete determination of the solid (RI)-liquid equilibria of four consecutive n-alkane ternary systems in the range C14H30-C21H44 using only binary data

Abstract

The liquidus surfaces and thermal windows of four ternary systems implying consecutive n-alkanes (for n between 14 and 21 carbon atoms) have been studied combining Differential Scanning Calorimetry (DSC), X-ray experiments, and calculation using the program Txy-CALC. From the DSC measurements, the transition temperatures as well as the melting enthalpies have been determined. X-ray experiments performed at temperatures just below melting have shown that there is almost complete syncrystallization in the rotator form RI. The calculation of the RI –> L liquidus surfaces has been made with temperature-independent as well as temperature-dependent excess Gibbs energies. In both cases, the agreement between experimental and calculated data is very good, the average temperature difference being within the uncertainty of the former.Key words: n-alkanes, ternary mixtures, liquidus and solidus surfaces, rotator phase, thermodynamic analysis.