Chemical Characterization of GPC Fractions of Athabasca Bitumen Asphaltenes Isolated before and after Thermal Treatment

Abstract

The object of this work was to determine whether new information could be obtained by using gel permeation chromatography (GPC) to fractionate asphaltene samples prior to analysis. In particular, GPC elution profiles, elemental analyses, molecular weights by vapor pressure osmometry (VPO), and boiling point distributions of the asphaltenes isolated from the original Athabasca bitumen feed (Feed) and from its total liquid product (TLP) after visbreaking were compared. The analyses showed that for GPC run using chloroform, fractionation was based on size where elemental analyses and boiling point distributions indicated that the earlier eluting fractions were not aggregates of later eluting fractions. The largest TLP asphaltene species were slightly smaller in size (by GPC and VPO) to those in the Feed asphaltenes; the smallest TLP asphaltene species were smaller than those isolated from the Feed asphaltenes and contained material with an initial boiling point of 340 °C despite both vacuum distillation (524 °C cutpoint) and pentane extraction being used during asphaltene preparation. For comparable molecular sizes by GPC and VPO, the TLP asphaltene fractions had lower H/C ratios and so were more aromatic and consisted of higher boiling material than the Feed asphaltene fractions. VPO results and elemental analysis trends confirmed that pentane extraction leaves behind molecules (asphaltenes) on the basis of some combination of size, aromatic content, and polarity. The significance of the various fractions of asphaltene species isolated remains to be evaluated in terms of their contributions to bitumen and heavy oil behavior during both production and thermal processing.

New Pathways for Asphaltenes Upgrading Using the Oxy-Cracking Process

“…Typical functional chemical shifts in 1 H NMR such as terminal alkyl methyl (0.9 ppm), alkyl methylene groups (2.0 ppm), and methylene bonded to the aromatic groups (2.7 ppm) as well as aromatic molecules (7–8 ppm) have been observed in asphaltene and/or dissolved aquatic organic materials . The assignation of the major oxygenated functional groups was possible through previous reports: , a methyl group from an aromatic ester (2.3 ppm), a methoxy group bonded to a monoaromatic (4.0 ppm).…”

“…Typical functional chemical shifts in 1 H NMR such as terminal alkyl methyl (0.9 ppm), alkyl methylene groups (2.0 ppm), and methylene bonded to the aromatic groups (2.7 ppm) as well as aromatic molecules (7−8 ppm) have been observed in asphaltene 49 and/or dissolved aquatic organic C−H bends); 3) Aliphatics (3: stretches, 3′: bends); 4). CO aldehydes; 5).…”

Organic carbon hidden in urban ecosystems

“…The high soil OC concentrations were attributed to soil contamination with bitumen. The standard loss on ignition temperature of 450°C was reduced to 340°C, as this temperature that does not volatilize bitumen57, the main constituents of which have boiling points above 500°C57 but it does oxidise the majority of OC29. This is a conservative approach that will tend to underestimate rather than overestimate organic carbon in this rather small group of samples which present significant challenges for accurate OC measurements.…”

Composition of Initiated Cracking Products of High-sulfur Natural Bitumen

“…Amount of resins and asphaltenes defines bitumen properties of both dispersion medium and dispersed phase, as well as natural bitumen aggregate stability of in the thermolysis conditions [2][3][4][5][6][7] . These compounds have high molecular weight, tend to condense and coke formation during processing, and deactivate catalysts [8][9][10] .…”