Biotechnological Upgrading of Petroleum

Abstract

The focus on upgrading petroleum has been on sulfur, but the ability to metabolize organonitrogen compounds may be particularly important because organonitrogen compounds are associated with the majority of metals in petroleum. Sulfur is present in crude oil almost exclusively as organic sulfur. While there are multiple types of organosulfur compounds, such as mercaptans, sulfides, disulfides, and thiophenes, the most abundant form of sulfur in petroleum is usually thiophenic. Thiophenic sulfur often comprises 50 to 95% of the sulfur in crude oil and petroleum products, and alkylated derivatives of dibenzothiophene (DBT) are the most common organosulfur compounds typically found in crude oil and diesel. Integrating a biodesulfurization process into a refinery is the only way to treat a product such as diesel. Biodesulfurization could fit well with current practices in the petroleum industry if performed in conjunction with desalting and dewatering operations. The removal of organically bound nitrogen from petroleum without the loss of significant calorific value requires the selective cleavage of carbon-nitrogen bonds. The sulfur and nitrogen content is of environmental concern, due to potential sulfurous and nitrous emissions from petroleum combustion. Metals, and to a lesser extent sulfur and nitrogen, present in heavy crude oils can contaminate catalysts used in hydrodesulfurization, limiting the effectiveness of current technologies to remove sulfur and nitrogen from these oils.