Effects of Temperature and Pressure on Asphaltenes Agglomeration in Toluene. A Light, X-ray, and Neutron Scattering Investigation

TLDR

The study employed SAXS, SANS, and DLS to probe how temperature and pressure influence asphaltene aggregate sizes in toluene across a wide size range. As temperature decreases, asphaltenes irreversibly aggregate into much larger particles, while at higher temperatures aggregation is reversible and yields small stable entities; pressure has a negligible effect compared to temperature.

Abstract

Small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS), and dynamic light scattering (DLS) are used to study the temperature dependence of asphaltene aggregate sizes in toluene solutions. A large range of aggregate sizes is covered by combining the three scattering methods. The effect of temperature on aggregate size is also investigated over a considerable temperature range. A huge modification of asphaltene macrostructure is observed. At high temperatures, reversible aggregation of asphaltene leads to stable small entities. When decreasing the temperature, irreversible aggregation of asphaltene occurs, corresponding to a large increase of the aggregate size. We have also investigated the effect of pressure on asphaltene solution in toluene as a function of temperature. Our results indicate that pressure has a minor effect, which is much less important than that of temperature, on the weight of the asphaltene aggregates.