Properties of GPC separated maltene fractions derived from Utah and Athabasca bitumen

This work deals with bitumens derived from two different types of oil sands: 1) Athabasca from the HcHurray formation in Alberta, Canada and 2) from the Unita basin in the green River formation, Utah, USA. Maltenes separated from these two bitumen were fractionated by Gel Permeation Chromatography (GPC) into fractions having number average molecular weights in the range from 289 to 5831 for Athabasca and from 300 to 11985 for Utah maltenes. The fractions obtained were examined by vapor pressure osmometry, absorption spectrometry in the visible region as well as proton and 13C NMR. Utah fractions were more aliphatic with longer average aliphatic chain length. Branched and alicyclic types were more abundant in the Utah samples, especially those of low MW. There was an apparent difference in the hydrocarbon structure of both maltene GPC fractions at MW approximating 800. An abrupt change in the correlation between the light absorbing parameter K500/Ksoo and molecular weight at MW approximating 800 was also observed. It is suggested that these rapid changes provide a convenient means of dividing the maltenes into two classes which may be used to characterize the maltenes of heavy oils and bitumens derived from various sources.