Emerging Role of Biorefining of Heavier Crude Oils and Integration of Biorefining with Petroleum Refineries in the Future

Abstract

Abstract With the depletion of light and sweet crude oils, reliance and dependence on heavier crude oils will increase. However, refining of heavier crudes generates not only larger amounts of heavier products, but is also costly and involves problems of corrosion of equipment and poisoning of costly catalysts. Presence of asphaltenes, asphaltols, S-heterocyclics, N-heterocyclics, organometallics, and metal sulphides, in crude oils results in poisoning of costly catalysts used for FCC and hydrocracking. Thus, there is a need to remove sulfur, nitrogen, and toxic metals from heavier crude oils and also a necessity of degrading larger higher molecular weight-bearing complex molecules to lower molecular weight-bearing lighter crudes. Conventional physical and chemical refining techniques may not be easily applied to heavier crudes. Thus, there is a need to develop simpler biorefining techniques to not only biodegrade the heavier asphaltenes and asphaltols, but also to remove sulfur, nitrogen, and toxic metals from crude oils. This paper describes the studies of biorefining of crude oils, diesel, and gasoline, which includes studies on microbial degradation, biodesulfurization, biodenitrogenation, and biodemetallation of crude oil using not only mesophilic, but also thermophilic bacteria. The role of microbial isolation from geographically diverse sites, chemotaxis, and genetic engineering tools, such as gene conversion, gene duplication, transportation, and biovehicles (plasmids and transposons) and rearrangement of DNA fragments, is vital in these studies. There is a need to genetically develop a designer microbe which can help in biorefining of heavier crude oils efficiently and economically. Bioprocess engineering of heavier crudes may include pre-biorefining, during-biorefining, and post-biorefining techniques. In the future, an integration of biorefining with petroleum refining by rendering not only heavier crudes as lighter crudes through microbial degradation, but also through biodesulfurization, biodenitrogenation, and biodemetallation may be required.