Process Considerations in the Biodesulfurization of Crude Oil

Biodesulfurization offers an attractive alternative to conventional hydrodesulfurization due to the mild operating conditions and reaction specificity afforded by the biocatalyst. The enzymatic pathway existing in Rhodococcus has been demonstrated to oxidatively desulfurize the organic sulfur occurring in dibenzothiophene while leaving the hydrocarbon intact. In order for biodesulfurization to realize commercial success, a variety of process considerations must be addressed including reaction rate, emulsion formation and breakage, biocatalyst recovery, and both gas and liquid mass transport. This study compares batch stirred to electro-spray bioreactors in the biodesulfurization of both model organics and actual crudes in terms of their operating costs, ability to make and break emulsions, ability to effect efficient reaction rates and enhance mass transport. Further, sulfur speciation in crude oil is assessed and compared to the sulfur specificity of currently available biocatalysts.