Effects of aromatics on desulfurization of liquid fuel by π-complexation and carbon adsorbents

Equilibrium adsorption of thiophenic sulfur compounds, thiophene (T), benzothiophene (BT), and dibenzothiophene (DBT), from their binary solutions in n-octane and ternary solutions in n-octane and benzene, on three sorbents (activated carbon (AC), AgNO3/MCM-41 and Cu(I)–Y) were studied systematically. Fixed-bed adsorption/breakthrough experiments on these sorbents were also carried out. For all thiophenic sulfur compounds in both binary and ternary solutions, the sorbent adsorption capacities followed the order: Cu(I)–Y>AgNO3/MCM-41>AC. For each sorbent, the selectivity of adsorption of thiophenic sulfur compounds from liquid solutions followed the order: DBT>BT>T>benzene. The experimental results were well interpreted by molecular orbital calculation results. For ternary solutions, benzene competed against thiophenic sulfur compounds for adsorption sites, resulting in reduced thiophenic sulfur adsorption on the studied sorbents. Based on the single-solute Langmuir–Freundlich isotherms, the extended Langmuir–Freundlich isotherm (for multi-component equilibrium adsorption) was used to predict adsorption in ternary solutions, which was in fair agreement with the experimental results. The Cu(I)–Y sorbent was fully regenerable.

► Adsorption and breakthrough on three sulfur compounds over three sorbents were studied. ► A basic understanding of the effects of aromatics on desulfurization was provided. ► Langmuir–Freundlich isotherm can predict adsorption of sulfur in ternary solutions. ► The desulfurization results were interpreted by ab initio molecular orbital calculations.