(189z) Preparation, Characterization and Adsorption Study of Ag-TiO2 Sorbent for Removal of Sulfur Organic Compounds from Fuels

Samokhvalov, A., Auburn University
Nair, S., Center for Microfibrous Materials Manufacturing, Department of Chemical Engineering, Auburn University, Auburn, AL
Davis, Z., Auburn University
Duin, E., Auburn University

The Ag/TiO2-based adsorbent for selective removal of sulfur-containing impurities from logistic fuels was prepared by incipient wetness impregnation of commercial titania with AgNO3 precursor with the subsequent calcination, and characterized. The survey XPS spectra show Ag, Ti, O and spurious C as expected. No N is found, indicating complete decomposition of Ag precursor. The XRay Diffraction (XRD) finds no metallic Ag, suggesting that Ag may be present only as ions and/or nanoparticles. The energies of Auger M4N45N45 and XPS 3d5/2 lines are used to calculate the Auger parameter α for Ag. Based on the value of α, silver is present mainly as Ag+1. The latter finding is independently confirmed by the Electron Spin Resonance (ESR) Spectroscopy. The vast majority of all Ag in the sorbent is in the diamagnetic (Ag+1) form, with only minor concentrations (~0.1% of total) as paramagnetic Ag2+. The Ti is present mainly as diamagnetic Ti4+. Adsorption and desorption of few representative S-containing Polyaromatic Hydrocarbons (PAHS) typically present in petroleum-derived fuels ? Thiophene (T), Benzothiophene (BT) and Dibenzothiophene (DBT) - on the surface of the sorbent was studied by the Temperature-Programmed Desorption (TPD). Significant fraction of adsorbed Thiophene (T) binds reversibly and desorbs without decomposition at ~370 K. At higher temperatures, the rest of adsorbed T reacts by C-S bond scission, forming low molecular weight products: butadiene C4H6, SO2 and H2S. Benzothiophene (BT) adsorbs only weakly (?physisorption?). DibenzoThiophene (DBT) adsorbs only via ?chemisorption?. During TPD of DBT, C-S bond scission of surface-bound DBT occurs producing Biphenyl (BP). At higher temperatures (~700 K), strong SO2 desorption occurs for DBT, suggesting oxidation of surface silver sulfide formed as intermediate.


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