Room temperature aerobic oxidation of thiophenes catalyzed by silver 5-atoms clusters

Abstract

To produce an impact in the reduction of sulfur derivatives on the environment it is essential to further eliminate the sulfur content in fuels. Although oxidative desulfurization using low temperatures and atmospheric pressure is a very appealing alternative to the currently used, and highly energy demanding, hydrodesulfurization method, it suffers from the use of high amounts of oxidizing agents such as NO₂, H₂O₂, and tert-butyl-hydro-peroxide, especially for the oxidation of highly oxidation-resistant compounds as thiophens. Using X-ray absorption near edge structure (XANES) spectroscopy, we show that Ag clusters of 5 atoms (Ag5) have high catalytic activities to achieve the complete oxidation (S⁻² to S⁺⁶) of highly oxidation-resistant compounds, such as dibenzothiophene, tetraphenyl thiophene and asphaltene, under ambient conditions in a simple and efficient process. Additionally, an analysis regarding the effect of Ag5 concentration for possible oxidation routes for dibenzothiophene is shown. These results can open a new avenue to face the challenge of reducing the presence of sulfur compounds in fuels using simple and green approaches.