Desulfurization of high-sulfur jet fuel by mesoporous π-complexation adsorbents

Desulfurization of JP-5 jet fuel (1172 ppmw S) was investigated by π-complexation adsorption with AgNO₃ supported on mesoporous silica SBA-15 and MCM-41. The average pore sizes of AgNO₃/SBA-15 and AgNO₃/MCM-41 were 48.8 and 19.1 Å, respectively. The results of JP-5 desulfurization showed that significant sulfur breakthrough occurred at ∼10.0 and ∼15.0 mL/g by AgNO₃/SBA-15 and AgNO₃/MCM-41, respectively, at a space velocity of 1.25 h^-1. The spent AgNO₃/MCM-41 was regenerated by a simple process (heating in air at 200 °C) and ∼50% of the sulfur capacity was recovered after the first cycle. Molecular orbital calculations show that Cu⁺ (as that in CuY zeolite) formed stronger π-complexation bonding with the thiophenic compounds than Ag⁺ (in AgNO₃), as evidenced by experimental heats of adsorption. However, pore diffusion limitation of the large sulfur molecules (alkylated benzothiophenes) became an important factor for desulfurization of high sulfur jet fuels such that the AgNO₃-supported mesoporous sorbents yielded substantially better results than Cu(I)Y, although Cu(I)Y was better for a model fuel that contained only small sulfur molecules. Among all sorbents that have been investigated, the AgNO₃/MCM-41 sorbent showed the best desulfurization performance for high sulfur jet fuels.