Solid Petroleum Asphaltenes Seem Surrounded by Alkyl Layers

Abstract

In this review, a comprehensive analysis of recent results obtained in our laboratory and published in the literature is presented, which points toward the existence of alkyl layers surrounding precipitated asphaltene solids. A micellar model for asphaltenes has been proposed, which explains many of the experimental determinations carried out to date with these compounds. The model considers the existence of alkyl moieties surrounding the inner aromatic cores. Faster dissolution kinetics of asphaltenes modified by coprecipitated waxes has been explained by the enhanced incorporation of alkane-surrounded particles into the eluent employed in the dissolution experiments. Finally, asphaltene volumetric changes brought by organic solvents have recently been studied, and can be explained by the existence of an alkyl layer prone to the incorporation of solvent molecules. This paper will discuss these aspects that seem to support the model long time ago postulated by Yen and coworkers.

Acknowledgments

Funding and permission for publication provided by PDVSA-Intevep is greatly appreciated. Helpful discussions held with M. C. Garcia, O. Leon, and M. Orea from PDVSA-Intevep are deemed very important for this work. Analytical support provided by Lola de Lima was greatly appreciated. Dr. Irwin WieheÇs encouragement to write the article was greatly appreciated.