Structural Effects of Nonionic Surfactants on Their Ability to Reduce the Dissolution Pressures of Heavy Hydrocarbons in Supercritical CO₂

Abstract

The effects of selected nonionic surfactants on dissolution pressures of the octacosane and hydrocarbon mixtures in supercritical CO2 (scCO2) were investigated at 318–343 K to study relationships between the structures of the surfactants and their ability to improve solubility. Dissolution pressures of the solutes were experimentally observed to be decreased by at most 11.10% and at least 0.44% in the presence of the surfactants. However, this solubility‐improving performance was diminished with an increase in the molecular chain length of the surfactant. Linear surfactants gave better solubility‐improving performances in the octacosane/scCO2 systems, while branched compounds were better in the hydrocarbon mixture/scCO2 systems, which are attributed to the similarity of the chain length between the surfactant and the solute. X‐ray computed tomography tests provided evidence for direct material exchange between the hydrocarbon mixture and scCO2.