Thermodynamics of the Deposition of Complex Waxes and Asphaltenes in Crude Oil

The thermodynamics of wax formation in crude oils is examined and additional insights obtained into the problem. We show that a correlation for cloud point, or wax apppearance temperature, obtained for pure-substance waxes may be extended to mixtures of hydrocarbons, thereby generalising the usefulness of the correlation. We apply the colligative equation for freezing point depression to quantify the analogous activity of wax inhibitors. The limits of applicability of an empirical formula that relates wax molecular weight and wax density are examined. We extend the analysis to the high molecular weight asphaltenes.