The Role of n-Alkane Solvent Carbon Number on the Gelation of Long-Chained n-Alkanes in Solution

Crystallization and subsequent gelation of n-alkanes in subsea oil pipelines is an issue of great economic importance to the petroleum industry. To develop better wax remediation strategies, is of interest to gain a better understanding of how n-alkanes crystallize in gel in solution. In this work, the role of the solvent on gelation properties was explored. Model oil solutions containing one or two long chain n-alkanes (carbon numbers of 28, 32 and 36) solutes were dissolved at varying wax fractions in short chain n-alkanes (carbon numbers of 7, 10, 12 and 16). The cloud points, gel points and pour points were measured for these solutions. Results showed that all of the cloud points could be condensed into one relationship using only the mole fraction of the least soluble solute, a result of the solutions all following ideal solution theory. Rheometric results were consistent for samples where the solvent was decane or dodecane. However, hexadecane samples provided results that were much different, an indication that the chain length of the solvent can play a role in the formation of a gel. It is hypothesized that the difference between the trends seen is caused by differences in how the crystals nucleate, grow and aggregate.