Desulfurization Sans Catalysts

Two research teams report catalyst-free approaches to reducing the concentration of sulfur compounds in transportation fuels. Dimethyldibenzothiophene (DMDBT) and related compounds deactivate automobile catalytic converters and play a role in causing acid rain. Oil refiners strip the bulk of these compounds from fuels by using hydrodesulfurization, a catalytic process that volatilizes the sulfurous materials by reacting them with hydrogen at high temperature and pressure. The companies still face challenges in removing sulfur from fuels because of tougher automobile emissions standards and the growing use of lower grade crude oil. Michiel Makkee of Delft University of Technology, in the Netherlands, and coworkers now report that γ-butyrolactone can be used under mild conditions to facilitate selective air oxidation of sulfur compounds in fuels and oils to sulfones (ChemSusChem, DOI: 10.1002/cssc.200800109). The sulfones are easily separated from the lactone phase, and the lactone can be reused. Separately, Jalal Shayegan and coworkers at Sharif University of Technology, in Iran, have shown for the first time that a fungus—a Stachybotrys species—effectively removes sulfur compounds (65 to 76%) from heavy crude oil samples at just 30 ºC (Ind. Eng. Chem. Res. 2008, 47, 7476).