Neutron total scattering from solid Athasbasca asphaltenes and Athabasca asphaltenes dissolved in 1-methylnaphthalene-d10 at 25wt% measured on NIMROD

Abstract

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).