Poster Session

Reversible Sorption of Athabasca Bitumen Constituents on Metal, Metal Oxide and Mineral Surfaces

Cheng Xing, PhD student in Chemical Engineering

Supervisor - Dr. John Shaw

Asphaltene deposition occurs in hydrocarbon resource production, transport and refining. Paradoxically, the worst fouling problems tend to arise from low asphaltene content fluids. Fouling conditions arise in both current and proposed bitumen production (e.g.: VAPEX) and refining (e.g.: solvent de-asphalting) technologies where the bitumen is diluted as a normal part of the process operation. Previous work by our group has shown that a thin sticky deposit forms on stainless steel surfaces when exposed to Athabasca bitumen vacuum residue (ABVB) + pentane mixtures. The problem is worst at low ABVB mass fraction where at 5 wt % the reversible deposition boundary is at ~ 150 C. As the ABVB mass fraction is increased, the threshold temperature decreases to near room temperature. Only at more than 50 wt % ABVB does the threshold temperature begin to increase again, this time because the hydrocarbon medium itself is becoming semi-solid.

In this exploratory experimental project, the composition of the deposit on well characterized surfaces is addressed for the mixture cited above. A sputtering system is used to create well-defined surfaces on silicon wafers. Surface compositions were then analyzed (XPS) prior to and subsequent to exposure to ABVB + pentane mixtures at 125C. The preliminary results show that asphaltenes are not deposited on the substrate.