Sorting Sulfides

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Science  28 Apr 2006:
Vol. 312, Issue 5773, pp. 501
DOI: 10.1126/science.312.5773.501a

The abundant organosulfur compounds in crude oil are oxidized to acidic pollutants (such as sulfuric acid) during combustion. To minimize their environmental impact, gasoline and diesel are subjected to desulfurization processes before use. However, tighter regulations have spurred chemists to pursue more efficient desulfurization methods, which would treat heavy oil before the cracking process that yields transportation fuels.

Toward this end, Choudhary et al. present a screening method to differentiate and quantify the organosulfur components of heavy oil. They first assay the aliphatic compounds by selective oxidation, followed by chromatographic/mass spectral analysis of the aromatics. Components are classified based on size and structure (mono- to hexacyclic, compact or extended geometry), and the relative reactivities of each class are then compared under varying desulfurization conditions. They find, for example, that phenanthrothiophenes are the least reactive toward hydrogenolysis (reductive removal of the sulfur as H2S) at 622 K but relatively more reactive at 655 K. They also determine which aromatics accept hydrogen more rapidly at carbon than at sulfur. These data offer useful projections for large-scale process optimizations. — JSY

Angew. Chem. Int. Ed. 45, 10.1002/anie.200503660 (2006).

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