Mechanism of Sulfur Removal in Adsorptive Desulfurization of Hydrocarbon Fuels Using Ag-Titania Sorbents

Silver supported on titanium oxide have regenerable adsorption sulfur capacity for liquid fuels at ambient conditions. Mechanistic details of sulfur removal were obtained through observation of breakthrough of sulfur aromatics varying in structure with respect to aromaticity, alkyl side chains etc. Sulfur-free aromatics with the most basic sulfur heteroatoms demonstrated the highest capacity indicating that the active centers were acidic in nature. Adsorption centers were deactivated when samples were treated with basic probe molecules. Infrared spectroscopy was used to identify the structure of resulting surface complexes. These activities identified bronsted acid centers as the active centers for sulfur removal in Ag/TiO2 sorbents. Equilibrium isotherms established for various aromatic sulfur molecules demonstrated a reasonable fit for the Langmuir adsorption model. Sulfur removal was therefore attributed to physical adsorption.