MOLECULAR-WEIGHT PROPERTIES OF ASPHALTENES CALCULATED FROM GPC DATA FOR OCTYLATED ASPHALTENES

Octylated asphaltenes (OA), and hexane-soluble n-octyl derivatives of asphaltenes, have been used for the determination of more realistic mo lecular weight averages and molecular weight distributions (MWD) of as phaltenes. Here we report the synthesis and characterization of the Ha maca OA. Both C-13 and elemental analyses show that about five n-octyl groups per 100 carbon atoms are incorporated into Hamaca asphaltenes. When GPC columns are calibrated with monodisperse octylated asphalten e standards (OAS), the M-n value obtained for Hamaca OA was equal to t he one measured by VPO. From this information, and from the GPC result s and the above calibration, the MW range (50000-300), M-n (2250) and M-w (6000) values were calculated for the above asphaltenes. (C) 1998 Elsevier Science Ltd. All rights reserved.