Deep-Vacuum Fractionation of Heavy Oil and Bitumen, Part II: Interconversion Method

In Part I of this two-part series, a recently developed deep-vacuum fractionation apparatus (DVFA-II) was standardized and used to fractionate heavy oil samples by boiling point at a pressure below 1 Pa. Up to 50 wt % of a Western Canadian bitumen was distilled, compared with 26 wt % distilled with conventional spinning band distillation (SBD), and eight cuts were recovered. Here, an interconversion technique is developed to determine the normal boiling point (NBP) curve from the low-pressure boiling point data collected using DVFA-II. A simultaneous correlation of vapor pressure and heat capacity data based on the Clapeyron equation was used to determine the NBP of each cut. Of the vapor pressure correlations considered, the three-parameter Cox equation best fit the data, with average absolute relative deviations within 7% and 1% for the vapor pressure and heat capacity data (Δ C ′ exp ), respectively. The estimated maximum and minimum errors in the calculated NBPs were 2.2% and −2.5% (8 and 9 K), respectively, and the calculated NBPs were within 2% of the SBD data. It was demonstrated that the distillation data for a heavy oil sample follow a Gaussian distribution and therefore that the NBP curve of heavy oil maltenes can be represented well using a Gaussian extrapolation.