Neutron total scattering from solid Athasbasca asphaltenes and Athabasca asphaltenes dissolved in 1-methylnaphthalene-d10 at 25wt% measured on NIMROD
Neutron total scattering from solid Athasbasca asphaltenes measured on NIMROD. Asphaltenes were precipitated from Athabasca bitumen by the addition of heptane at a ratio of 40:1 by weight. The mixture was homogenized by stirring for 24 h, and the asphaltenes were separated by centrifugation at 3472g for 10 min. Solid asphaltenes were washed for 24 h in a Soxhlet extractor with pure heptane and then dried in vacuum oven at 80 °C for 4 days. Because Athabasca bitumen contains inorganic solids, an additional step was taken to isolate the asphaltenes. The solid asphaltene samples were diluted to a 4.8 wt % solution in toluene and centrifuged at 5000g for 270 min to remove the inorganic solids. The toluene was then removed by forced convection and then subsequent drying in a vacuum oven at 80 °C to obtain the solid asphaltene sample used for experimentation. Solution samples were re-dissolved in the appropriate mass of deuterated 1-methylnaphtalene at elevated temperature using a stirrer/hotplate. The sample was contained in a TiZr cell (1mm path length for solutions, 2mm path length for solids) maintained at 20C or 180C using a circulating oil bath. The measured neutron scattering was reduced to the interference differential scattering cross section, F(Q), using the GudrunN program. This program merges the time-of-flight scattering from all detectors to a single Q scale, normalizes to a 3 mm VNb plate calibration standard, subtracts scattering from the sample container and empty instrument, and applies corrections for beam attenuation, multiple scattering and inelastic scattering (by use of an iterative correction).
National Science Foundation