New sorbents for desulfurization of liquid fuels by π-complexation

CuY and AgY zeolites were studied as selective sorbents for the desulfurization of liquid fuels. Thiophene and benzene were used as the model system, and vapor-phase isotherms were measured. Compared to NaY, CuY and AgY adsorbed significantly larger amounts of both thiophene and benzene at low pressures as a result of π-complexation with Cu⁺ and Ag⁺. On a per-cation basis, more thiophene was adsorbed by Cu⁺ than by Ag⁺, e.g., 0.92 molecule/Cu⁺ vs 0.42 molecule/Ag⁺ at 2 × 10^-5 atm and 120 °C. Molecular orbital calculations confirmed the relative strengths of π-complexation as thiophene > benzene and Cu⁺ > Ag⁺. The experimental heats of adsorption for π-complexation are in qualitative agreement with theoretical predictions.