Molecular structure and association behavior of petroleum asphaltene

Abstract

Asphaltenes, the most polar fraction in crude oil, are critical to all aspects of petroleum utilization. The strong interactions between asphaltenes lead to various levels of aggregation, which is responsible for a variety of transportation and upgrading problems. The structure and aggregation of asphaltene have received worldwide concerns, and a lot of efforts have been made to characterize asphaltene aggregates and related phenomena. The complexity of asphaltene composition makes it difficult to understand the true nature of aggregation. Advanced instruments have been applied to characterize the structure of asphaltenes and its aggregates and also their association behavior. The recent approaches on both analytical measurement and modeling lead to new insights into asphaltene structure and aggregation processes. This has led to new aggregate architecture and aggregation mechanisms. Modeling approaches were also used to predict association energies, aggregate size distribution, and phase behavior. A lot of model compounds have been synthesized or built on the computer to help understand the interaction between molecules. The results challenged the traditional view that heavy petroleum and asphaltene are ultra-large molecules. The asphaltenes are composed of numerous small molecules with strong molecular interactions which form complex nanoaggregates. In this review, we make a brief summary of the recent progress on molecular aggregation of asphaltene and discuss new theories, discoveries, and ongoing debates.