Chapter 4 Prospects for biological upgrading of heavy oils and asphaltenes

Publisher Summary This chapter discusses the characteristics of the molecules in the vacuum residue fraction of crude oils and examines the prospects for using biological processes to improve the value of these materials. Known interactions between microbes and the high molecular weight components of crude oils include oxidation of aliphatic and aromatic carbon groups, oxidation of naphthenic acids, and oxidation and desulfurization of aromatic and aliphatic sulfur groups. Hydrogenation and dehydrogenation reactions have been demonstrated only on lower-molecular weight components. All of these reactions are of potential interest for upgrading heavy crude oils and bitumens, but a major barrier is the transport of reactants to the active site of reaction, particularly for intracellular enzymes in bacteria. Although membranes may give significant barriers for bioprocessing of heavy hydrocarbons, the interactions of cell membranes with oil/water interfaces may be of interest in de-emulsifying oil and dispersing asphaltenic material to prevent deposition.