Comparison of Bitumen Fractionation Methods

Several preparative bitumen fractionation methods based on initial precipitation of asphaltenes by an n-paraffin followed by solvent elution from silica gel and refluxing on Attapulgus clay are reviewed. These methods are based on the ASTM D2007 standard and have been collectively designated as SARA (saturates, aromatics, resins, asphaltenes). In actual fact, there are numerous variations of SARA. In this paper, the results from the standard ASTM method are compared to a variation developed by Syncrude. One alternative to SARA was developed at Alberta Research Council (ARC) and is called SAPA (saturates, aromatics, polars, asphaltenes). It is compared to SARA, and some advantages and disadvantages of each are described. An analytical thin layer chromatographic (TLC) method, producing only component-type data, was also developed at ARC as a faster alternative to SAPA. The TLC approach has recently been modified to produce results similar to those of SAPA, in order that the results from the two techniques may be used interchangeably. Results and comparisons between SAPA and TLC will be described for two different bitumen samples.