(330b) Co-Aggregation of Asphaltenes and Inorganic Solids in Diluted Bitumen

Authors: 
Kong, W., University of Utah
Martineau, J., The University of Utah
Yang, Y., University of Utah
Zhang, J., University of Utah
Knapper, B., Syncrude Canada Limited
Ng, S., Syncrude Canada
Hoepfner, M. P., The University of Utah

Athabasca bitumen contains over 10% asphaltenes and around 1% inorganic solids following the froth extraction process. Asphaltenes are a class of large aromatic organic compounds. A recent study found that the asphaltene precipitation rate increases significantly when inorganic solids were present in the mixture. [1] The results were modeled as the inorganic solids acting as collection sites for asphaltenes, which allowed them to be more easily separated by centrifugation. This new observation opens up new areas of study; specifically, determining the role of asphaltene adsorption onto solid surfaces during the dynamic process of phase separation. In this study, we aim to investigate the structure of asphaltenes and inorganic solid clusters that form during precipitation to determine the aggregation mechanism and dynamics. Athabasca bitumen was diluted with a heptane-toluene blend at low concentrations to promote asphaltene adsorption onto solid surfaces, but below the asphaltene bulk phase transition. After waiting different durations, additional heptane-toluene diluent was added to precipitate asphaltenes. The rate and quantity of solids collected was recorded. Additionally, the precipitated clusters were cut by focused ion beam (FIB) milling and images were taken by scanning electron microscopy (SEM). A large quantity of non-uniformly distributed ultra-fine solids (<200nm) were found in the precipitated asphaltenes clusters. A greater quantity of inorganic solids were detected in samples that were aged for a longer time at the lower diluent ratio. These results suggest that ultra-fine solids aggregate with asphaltenes and create nano-scale clusters (<500nm) that then further interact through cluster-cluster aggregation (>1 micron). Additional investigation of the solids properties that promote association with asphaltenes during precipitation is ongoing.