Application of CO(2)-Switchable Oleic-Acid-Based Surfactant for Reducing Viscosity of Heavy Oil

CO(2)-switchable oligomeric surfactants have good viscosity-reducing properties; however, the complex synthesis of surfactants limits their application. In this study, a CO(2)-switchable “pseudo”-tetrameric surfactant oleic acid (OA)/cyclic polyamine (cyclen) was prepared by simple mixing and subsequently used to reduce the viscosity of heavy oil. The surface activity of OA/cyclen was explored by a surface tensiometer and a potential for viscosity reduction was revealed. The CO(2) switchability of OA/cyclen was investigated by alternately introducing CO(2) and N(2), and OA/cyclen was confirmed to exhibit a reversible CO(2)-switching performance. The emulsification and viscosity reduction analyses elucidated that a molar ratio of OA/cyclen of 4:1 formed the “pseudo”-tetrameric surfactants, and the emulsions of water and heavy oil with OA/cyclen have good stability and low viscosity and can be destabilized quickly by introducing CO(2). The findings reported in this study reveal that it is feasible to prepare CO(2)-switchable pseudo-tetrameric surfactants with viscosity-reducing properties by simple mixing, thus providing a pathway for the emulsification and demulsification of heavy oil by using the CO(2)-switchable “pseudo”-oligomeric surfactants.