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NMR Finger Printing of Chemical Changes in Asphalt Fractions on Oxidation

Abstract The composition of asphalt has been the subject of much study because such data is required in determining its performance-related properties. A problem inherent in studying asphalt composition is its chemical complexity; however, the characterization of asphalt can better be achieved by separating it into fractions. In this work, the chemical property of commercial grade asphalt obtained from BAPCO refinery, Bahrain (BH) was studied. The rolling thin-film oven (RTFO), termed as short-term aging, and pressurized aging vessel (PAV), termed as long-term aging, tests were used to simulate the laboratory aging of this asphalt. The Corbett fractionation procedure was used to separate fresh and aged asphalt into four generic fractions such as asphaltenes, polar aromatics, naphthene aromatics, and saturates. Nuclear magnetic resonance (NMR) was employed to fingerprint the chemical changes that occurred in asphalt during the aging processes. NMR measurements of asphalt fractions showed that during aging, isomerization and dehydrogenation reactions took place. Significant differences were observed between the structure and composition of fresh and aged fractions of asphalt. The result from the NMR spectrometry has provided very significant information concerning the chemical transformations that occur during the aging processes.