(561e) Surface Science and Temperature Dependent ESR Spectroscopic Studies of Surface Chemical Reactions of Silver-Doped Titania with Thiophenes

Selective removal of PolyAromatic Sulfur Heterocycles (PASHs), including substituted thiophenes, from liquid fuels by sorption is promising emerging technology that could potentially be utilized in producing UltraLow Sulfur (ULS) fuels. We report here characterization of Ag-doped titania sorbent and studies of desorption of substituted thiophenes by temperature-dependent quasi-operando ESR and XPS. The Ag-doped titania prepared by impregnation, drying and calcination contains Ag as surface silver oxide, as found via XPS Auger parameter and confirmed by ESR. Model fuel mixtures of substituted PASHs (Thiophene, Benzothiophene, Dibenzothiophene, 4,6-Dibenzothiophene) in aliphatic hydrocarbon solvents (n-hexane, n-octane, n-dodecane) were adsorbed on Ag-doped titania. The temperature-dependent Quasi-Operando ESR study of the reactive suspension ?sorbent ? model fuel? was performed using the ?process-cool-measure-process? technique, with specimen heated by temperature controller, including reference measurements with the titania support. The ESR signal observed is attributed to the F-center, is present in both sorbent and titania support, does not change upon heating reactive suspensions up to 90 C, and interaction of supported Ag oxide with substituted thiophenes occurs without reduction or oxidation of silver ion. At higher temperatures, desorption of adsorbed thiophenes, oxidation of sulfur and reduction of silver ions take place, depending on molecular structure of the PASHs.