Experimental Determination and Representation of Binary and Ternary Diagrams of N-Hexacosane, N-Octacosane and N-Heptane

Accumulation of waxy deposits is a commonly occurring problem during exploitation and transportation of paraffinic crude oils. Limitation of these undesirable solids or removal by methods such as addition of chemical inhibitor, scrapping or heat tracing of flowlines, increase production costs. A better knowledge of this phenomenon will make it possible to adjust process operating parameters and limit the operating costs. Thermodynamic models can be used in order to calculate the wax appearance temperature and the amount of solid deposit versus temperature. In these models, the crude oil is represented as a mixture of pure or pseudo-components(which content several pure components). To describe the thermodynamic properties of those mixtures, data on pure components and on their mixtures are necessary but they are very scarce for heavy components in the literature. This work is devoted to the study of a mixture of heavy components including two heavy n-alkanes (n-hexacosane, denoted C26 and n-octacosane, denoted C28) and a solvent (n-heptane denoted C7). Measurements of solubility of C26 and C28 and of equimolar mixture of C26 and C28 in C7, and an isothermal ternary diagram of the mixture of the three components at 303K are presented. Their calculations using simple expressions of Gibbs molar energy (NRTL and Redlich-Kister) are in good agreement with experimental data. The work allows to consider calculating complex systems with the only use of binary interaction coefficients.