Application of spectral fluorescence microscopy for the characterization of Athabasca bitumen vacuum bottoms

The relationship between visible light region fluorescence properties and g ross chemical composition of ten narrow cut subfractions of Athabasca bitum en separated by super critical fluid extraction has been studied. The objec tive of this investigation was to evaluate the potential for utilizing spec tral fluorescence microscopy for empirically assaying the chemical composit ion (e.g. wt% saturates, aromatics, resins and asphaltenes) of the bitumen fractions. Two spectral parameters were used to characterize the bitumen fl uorescence properties: Lambda max (L-max in nm) or the wavelength of maximu m emission intensity, and Q, which is the ratio of intensity at 650 nm to t he intensity at 500 nm. Positive linear relationships with high r(2) values were established for L-max and Q parameters, which correlated with the wt% of resins plus asphaltenes, aromatic carbon, C/H atomic ratio and wt% of S , In addition, the fluorescence properties displayed a progressive red shif t to longer wavelengths, L-max and Q versus saturate/aromatic ratio and wt% saturates showed a negative linear relationship consisting of two distinct linear segments. Although L-max and Q increased up to about 550 nm and 1.0 , respectively, they showed a progressive red shift in the second segment t hat was accompanied by a decrease in both values. Weight per cent aromatics exhibited a polynomial (?) relationship with fluorescence properties, whic h may reflect variations in the proportion of mono- and di-aromatics relati ve to cata-condensed aromatics within the Athabasca bitumen subfractions. ( C) 2000 Elsevier Science Ltd. All rights reserved.