Association Behavior of Pyrene Compounds as Models for Asphaltenes

Energy Fuels, 19 (4), 1268 -1271, 2005

Association Behavior of Pyrene Compounds as Models for Asphaltenes

Kamran Akbarzadeh^§, David C. Bressler⁺, Jianing Wang⁺, Keith L. Gawrys^¥, Murray R. Gray⁺,* Peter K. Kilpatrick^¥, and Harvey W. Yarranton^§

⁺Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2G6, Canada

^§Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, Alberta T2N 1N4, Canada

^¥Department of Chemical Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905

Abstract:

Asphaltene association in solution has been studied extensively using methods such as vapor-pressure osmometry and neutron scattering. These methods give relative data on association as a function of solvent strength, temperature, and concentration, but interpretation of the results is hampered by the polyfunctional nature of asphaltenes and the distribution of molecular weight. In this work, we present data on association of representative model structures for asphaltenes, as measured using vapor-pressure osmometry in o-dichlorobenzene at 75-130° C, and using small-angle neutron scattering in toluene. A series of compounds were synthesized based on the four-ring aromatic compound pyrene. The synthetic compounds were designed to give interactions between aromatic rings, alkyl chains, and selected functional groups through aromatic interactions, hydrogen bonding, and polar interactions. Even in this strong solvent, polar interactions between oxygen functional groups gave average molecular weights of up to twice the true value, indicating dimer formation. An alkyl pyrene compound, dipyrenyl decane, gave much less significant association. Pyrene itself exhibited little or no self-association.