Asphaltenes: Definition, Properties, and Reactions of Model Compounds

The simple definition of asphaltenes—the material that dissolves in aromatic solvents and precipitates in normal alkanes—proved to be not very defining at all. The nature of this material, how it formed, what its key properties are, and how it behaves under thermal or catalytic reaction conditions has extensively evolved over decades of continuous research and debate. One of the main sources of the debate was the apparent conflicting findings between numerous analytical studies and thermal reaction studies of asphaltenes and their model compounds. Similar to the blind men describing different parts of an elephant, many studies were describing some aspect of the material as it is observed but not realizing the existence of a "larger" object, and even the observations were very subjective to how asphaltenes were precipitated and analyzed and how data was generated and interpreted. In this paper, a brief summary is given on how asphaltenes are defined, how they form, and the current consensus on their properties, and finally a focus on thermal behavior, as observed from thermal studies on asphaltenes and their model compounds. The collective knowledge from analytical and thermal studies on the asphaltenes and various model compounds helped settle most of the debate on the notoriously complex material named asphaltenes.