Design and technical evaluation of a conceptual process for transferring solvent precipitated asphaltenes into water utilising surfactant phase behaviour

Experiments are described which demonstrate that asphaltenes precipitated from a refinery tar using an excess of n-heptane spontaneously partition into a contacting water phase in the presence of an ethoxylated nonionic surfactant by effecting a temperature change. The process appears to be related to the temperature-dependent phase behaviour of the particular surfactant. Hot (ca. 80–90 °C) aqueous octa(ethyleneoxy) nonylphenylether (NPE8) and the heptane-diluted tar, were thoroughly and vigorously mixed for a short time and then allowed to stand and cool under quiescent conditions. A distinct oil/water interface rapidly appeared after the mixing had stopped and, at a specific temperature, asphaltene particles were observed to begin to “rain” into the lower aqueous phase, producing an aqueous asphaltene suspension. The temperature at which asphaltene transfer occurred was close to the phase inversion temperature of the NPE8/heptane system. Subsequent to different laboratory batch experiments, a larger-scale semi-continuous operation was carried out allowing other aspects of the process to be investigated. Rigorous economic analyses of the process have not been included in this study, although it is apparent that surfactant recycling would need to be ensured in order to approach commercial viability, even if the technical concepts translate well to large-scale operation.