Adsorption properties of organosulfur compounds on zeolite clusters: A density functional theory calculation study

The effects of cations of zeolite for the adsorption of organosulfur compounds were investigated by using density functional theory calculations. The binding energies of tetrahydrothiophene (C₄H₈S, THT), dimethyl sulfide (C₂H₆S, DMS), tert-butylmercaptan (C ₄H₁₀S, TBM), hydrogen sulfide (H₂S), and carbonyl sulfide (COS) on the zeolite model clusters [X(HO)₃SiOAl(OH) ₃, X = H⁺, Na⁺ and Ag⁺] were obtained and compared with those of H₂O, CO₂, and C ₁-C₃ light hydrocarbons. Compared to the H⁺ and Na⁺ cations, the Ag⁺ cation induces much stronger binding of THT, DMS, TBM, and H₂S over H₂O suggesting great enhancements in the adsorption selectivity. The order of binding energies of these sulfur compounds is THT > DMS > TBM > H₂S > COS, and it does not depend on the cation types. These results agree well with the experimental adsorption uptake and selectivity properties of AgNaY zeolites for organosulfur compounds.