ABSTRACT
Sulfur is a chemical element present in crude petroleum between approximately 100 and 33,000 ppm in its elemental as well as its chemically bound forms. In developed countries, there was recently a successful transition to environment-friendly ultralow-sulfur (ULS) ground transportation fuels with total sulfur at or below 30 ppmw. Nonreactive adsorption occurs when the molecule of an aromatic sulfur compound binds reversibly to the active site in the sorbent. Nonreactive desulfurization by adsorption is the most promising route toward commercialization. The mechanism of adsorption was studied using thiophene, the smallest molecule among aromatic sulfur compounds. The well-known 'conventional' sorbents for desulfurization by nonreactive adsorption are zeolites with supported cations of transition metals. In the majority of reported studies, the mesoporous metal-organic frameworks (MOFs) used for adsorption of the aromatic sulfur compound in solution contained transition metal (TM) cations as the coordinatively unsaturated site (CUS).
