l Davarpanah - Department of Chemical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran
f Vahabzadeh - Department of Chemical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran

Depletion of the conventional crude oil resources have generated attentions towards crude oil reserves and processing them. Large content of asphaltenes as the main chemical characteristic of a heavy oil causes the industry to face technological challenges in all phases of the operation: reservoir, transportation, and refining. Due to the strategic and economic reasons in area of pipeline transportation for instance, different methods have become practicable such as dilution, heat treatment, emulsion formation, partial upgrading, core annular flow, … . Structural characteristics with focusing on the asphaltenes are basis for any improvements in these techniques or even developing new methods. The purpose of the present work was to use nuclear magnetic resonance spectroscopy (NMR) and scanning electron microscopy (SEM) to structurally study asphaltenes extracted from off-shore Persian Gulf heavy crude oil using n-pentane and n-heptane as light alkane precipitants. Two important structural parameters of the asphaltenes were determined namely, the aromaticity (fa) and the average number of carbon atoms per alkyl side chain (ncarbon) where fa for n-C5 asphaltenes was lower (0.39) than that obtained with n-C7 solvent (0.49), while ncarbon parameter values were 7.7 and 5.7 for n-C5 and n-C7 asphaltenes, respectively. images developed using Scanning Electron Microscopy (SEM) showed some released particles on the surface of the asphaltenes, which may be indicative of resins desorption. Furthermore Structural characterization of asphaltene from heavy crude oil is important in different sectors of the petroleum industry and may provide rough estimate for the challenging position of this source relative to other geographically distributed heavy oil resources.

Asphaltenes, Heavy crude oil, NMR, Persian Gulf, SEM, Structural characterization,