Study on the dipole moment of asphaltene molecules through dielectric measuring

Long Li Zhang, Chao-he Yang, Ji Qian Wang, Guo Hua Yang, Li Li, Yan Vivian Li, Lawrence Cathles

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


The polarity of asphaltenes influences production, transportation, and refining of heavy oils. However, the dipole moment of asphaltene molecules is difficult to measure due to their complex composition and electromagnetic opaqueness. In this work, we present a convenient and efficient way to determine the dipole moment of asphaltene in solution by dielectric measurements alone without measurement of the refractive index. The dipole moment of n-heptane asphaltenes of Middle East atmospheric residue (MEAR) and Ta-He atmospheric residue (THAR) are measured within the temperature range of -60°C to 20°C. There is one dielectric loss peak in the measured solutions of the two types of asphaltene at the temperatures of -60°C or -40°C, indicating there is one type of dipole in the solution. Furthermore, there are two dielectric loss peaks in the measured solutions of the two kinds of asphaltene when the temperature rises above -5°C, indicating there are two types of dipoles corresponding to the two peaks. This phenomenon indicates that as the temperature increases above -5°C, the asphaltene molecules aggregate and present larger dipole moment values. The dipole moments of MEAR C7-asphaltene aggregates are up to 5 times larger than those before aggregation. On the other hand, the dipole moments of the THAR C7-asphaltene aggregates are only 3 times larger than those before aggregation. It will be demonstrated that this method is capable of simultaneously measuring multi dipoles in one solution, instead of obtaining only the mean dipole moment. In addition, this method can be used with a wide range of concentrations and temperatures.
Original languageEnglish (US)
Pages (from-to)609-615
Number of pages7
StatePublished - Jan 2015
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-C1-018-02
Acknowledgements: This publication was made possible by facilities created under Award No. KUS-C1-018-02 made by King Abdullah University of Science and Technology (KAUST). This work was partial supported by the National Science Fund Committee of China (20776160), and the Fundamental Research Funds for the Central Universities (14CX05029A). Thanks for Professor Kongshuang Zhao in Laboratory for Dielectric Relaxation Spectroscopy Analysis in Beijing Normal University for the valuable discussion.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.


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