Visbreaking Oilsands-Derived Bitumen in the Temperature Range of 340–400 °C

The low-temperature visbreaking of Canadian oilsands-derived bitumen was investigated. The objective was to determine the extent to which the fluidity of the bitumen can be improved by less-severe thermal conversion than normally employed industrially, while, at the same time, maintaining a high liquid yield. Most of the experimental work was conducted in the temperature range of 340–400 °C, although some data were also obtained at lower temperatures. It was possible to limit gas and coke formation and obtain a 96–97 wt % liquid yield, while decreasing the bitumen viscosity from ∼100 Pa s to 1 Pa s (measured at 40 °C). More remarkable was that viscosities of ∼3 Pa s could be obtained by just heating the bitumen to either 360 or 380 °C and then cooling it. The most plausible explanation for the rapid decrease in viscosity during low-temperature visbreaking was that there was a decrease in the effective volume fraction of the colloidal fraction. The viscosity change over time at constant temperature was complex, with at least one local minimum and maximum being observed. This aspect of the behavior could not yet be fully explained. Overall, it was found that the bitumen was reactive and that its thermal conversion behavior over the temperature range studied was comparable to that of a young crude oil, not a residuum.