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

Authors: 
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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