Studies of Athabasca asphaltene Langmuir films at air-water interface.
Asphaltenes are present in heavy oils and bitumen. They are a mixture of hydrocarbons having complex structures of polyaromatic rings and short side chains. In general, the high-molecular-weight asphaltene is the most aromatic fraction with the highest number of side chains and the low-molecular-weight asphaltene contains the lowest number of side chains, while the number of side chains of the whole asphaltene fraction lies in between. In this study, asphaltenes were extracted and/or fractionated from Athabasca oil sand bitumen. Subfractions of high and low molecular weight and the whole asphaltenes were characterized using a Langmuir trough and complementary techniques such as VPO, FTIR, AFM, and contact angle measurements. At an air-water interface, amphiphilic asphaltene molecules can form a monolayer. Various fractions (high, low, and whole) of the asphaltene molecules behave similarly at the air-water interface, characterized by close resemblance of their surface pressure-area, hysteresis, and relaxation isotherms. The high-molecular-weight asphaltene is the most expanded fraction, while the low-molecular-weight asphaltene fraction is the most condensed, with the whole asphaltene lying in between. At the air-water interface a monolayer of the low-molecular-weight asphaltene relaxes at a faster rate than one of the high-molecular-weight asphaltene.
Zhang
Li Yan
LY
Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2G5, Canada.
Lawrence
Steven
S
Xu
Zhenghe
Z
Masliyah
Jacob H
JH
D000388:Air; D000416:Alberta; D006841:Hydrocarbons, Aromatic / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D010578:Petroleum; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014867:Water
D006841:Hydrocarbons, Aromatic; D010578:Petroleum; D014867:Water