(620f) Adsorptive Desulfurization of Hydrocarbon Fuels by Ag/TiO2-Al2O3 Adsorbents: Mechanism of Sulfur Adsorption At Ambient Conditions

Sulfur removal by adsorption from liquid petroleum fuels at ambient conditions is a feasible approach for its low energy and zero hydrogen requirements. Silver supported on titania-alumina mixed oxide have demonstrated excellent regenerable sulfur adsorption capacity from hydrocarbon fuels at room temperature and pressure. In this work, the mechanism of sulfur adsorption onto mixed oxide supported silver adsorbent at ambient conditions was investigated.  Breakthrough experiments, N₂ physisorption, NH₃ chemisorption, and infrared (IR) studies were conducted to understand the adsorption phenomenon. In the breakthrough tests, model fuels consisting of various sulfur and non-sulfur species were used as challenges to investigate sulfur selectivity. Ammonia chemisorption was employed to classify different acid sites on the adsorbent surface. Ammonia, 2, 6-Lutidine, and trimethyl chlorosilane (TMCS) were adsorbed on the adsorbent surfaces as probe molecules and the resulting surface complexes were observed via IR. Titania dispersed alumina support provided the highest concentrations of acid centers over individual metal oxide supports. Increase in surface hydroxyl groups was observed after silver impregnation on the support. IR spectra of thiophene (T), benzothiophene (BT), dibenzothiophene (DBT), and 4, 6-dimethyldibenzothiophene (4, 6-DMDBT) treated adsorbentsamples revealed the presence of multiple sites for sulfur adsorption. There was less selectivity toward 4, 6-DMDBT because the attached methyl groups created steric hindrance. Both breakthrough and IR studies indicated that the sulfur compounds bind with the surface acid sites on silver adsorbent surface at ambient conditions.