The phase behavior of Athabasca vacuum bottoms (ABVB), a 798.15+ K (525+ °C) boiling fraction comprising 32 wt. % pentane asphaltenes, + pentane mixtures is elucidated using x-ray transmission tomography. These pseudo binary mixtures are models for the development of novel heavy oil/bitumen production and refining processes. Depending on the overall composition, these mixtures are shown to exhibit three and four phase equilibria including both expected (L1L2V) and unexpected (L2L3V) phase behavior separated by a small L1L2L3V zone. These multiphase equilibria provide challenges in production environments, where miscible flooding is typically desired, but afford new opportunities for the development of separation technologies in refining. Example pressure-temperature at constant composition phase diagrams and pressure-composition at constant temperature phase diagrams, which focus on the bubble pressure region where multiphase regions arise, are presented. Limited phase equilibria data sets for ABVB + heptane, decane and dodecane are also presented so that trends for ABVB + alkane mixtures with the size of the alkane diluent can be explored. We expect these phase diagrams to provide insights to heavy oil producers and refiners in addition to providing a benchmark for testing phase behaviour models for these and related complex hydrocarbon mixtures.

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