Heavy Oil Processing - Chemistry of Asphaltenes

From the title given to part IV of this book, it is obvious that in the next two chapters we will be engaged in studies involving the chemistry of the heaviest compounds of crude oil - asphaltenes. The presence of these compounds in crude oil leads to many problems during crude oil treatment. In this part of the book, these problems and ways to circumvent them are discussed. 

The present trend in the petroleum industry shows an increasing demand for light products such as gasoline, jet fuel and diesel fuel. In order to meet the market demand, refineries convert a portion of their residual heavy oils into light fractions by destructive processes as was highlighted in chapter 6. This conversion also results in the production of modem heavy fuels, which contain a greater concentration of sulfur, vanadium, and asphaltenes. 

Asphaltenes are considered to be part of the bottom of the barrel . They constitute the non-volatile, high molecular weight fraction of petroleum. In addition, since asphaltenes are non-soluble in heptane, they remain in the solid form in crude oil as well. 

The chemistry of asphaltenes is very complicated and it is the least studied field of crude oil chemistry. Because of the complexity of asphaltenes structure, there is no information about the exact chemical structure of an asphaltene molecule. It is natural that only the average asphaletene molecular is possible as given in the literature. The use of such a chemical structure (i.e. average molecular structure) for the asphaltene molecule is warranted because of the wide molecular weight range and the diversity of chemical groups in the structure of asphaltenes. 

The chemistry and understanding of the nature of asphaltenes is as fascinating as it is complicated. Many properties of asphaltenes are still not fully investigated. This, perhaps, is the object of the next generation of crude oil chemists that 

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