Normal alkanes, multialkane synthetic model mixtures, and real petroleum waxes: Crystallographic structures, thermodynamic properties, and crystallization

A general review is presented concerning jointly the crystallographic structures and the solid-solid and solid-liquid transition temperatures and enthalpies in the pure normal alkanes, as well as the structural and thermodynamic behavior of their synthetic binary, ternary, and multinary model mixtures and of real petroleum waxes. A major part of the structural and thermodynamic data of the literature, relative to the pure n-alkanes, are listed from methane up to the alkane with carbon atom number equal to 390. Variation relationships of the crystallographic long c-parameter that corresponds to the periodicity of the molecule layer packing along their axis, melting temperatures, and transition enthalpies are given as a function of the carbon atom number. The study of the literature on the n-alkane mixtures highlights the existence of isostructural binary, ternary, and multinary intermediate solid solutions which can be likened to a single pseudocomponent. This intermediate solid solution is equivalent to a hypothetical pure n-alkane whose carbon atom number is equal to the average carbon atom number of the mixtures. As a result, the solubility of these multinary solid solutions or real multiparaffinic waxes in linear, cyclic, or aromatic light solvents is identical to that of the pure n-alkanes: pseudobinary eutectic crystallization of the model or real wax as a single pseudocomponent on one hand and the light solvent on the other hand.