Molecular Weight Determination of Asphaltenes from Colombian Crudes by Size Exclusion Chromatography (SEC) and Vapor Pressure Osmometry (VPO)

摘要

Characterization of Colombian asphaltenes isolated from feedstocks to refining units was carried out during this study, emphasizing the determination of their average molecular weights (MW). Experimental conditions used for vapor pressure osmometry (VPO) and size exclusion chromatography (SEC) were investigated aiming to select the most suitable set up that affords the best representative values. SEC was observed to provide the most reasonable MW values, after analysis improvements were achieved by using realistic calibration curves got with phthalocyanines, compounds that closely mimic component structures within oil and asphaltenes fractions. MWs displayed by Colombian vacuum residua asphaltenes fall within the range 1,700 + -200 Daltons, reported previously for asphaltenes from different reservoirs worldwide.