Experimental and theoretical study of adsorptive interactions in diesel fuel desulfurization over Ag/MCM-41 adsorbent

Molecular dynamics simulation performed by the DFT/ONIOM method and X-ray photoemission spectroscopy (XPS) data were employed for studying the adsorbate-adsorbent interaction system in diesel desulfurization over Ag/MCM-41 produced from beach sand silica (MPI). The morphology and structure of the materials were characterized via powder X-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and field emission scanning electron microscopy (FESEM) together with energy dispersive spectrometry (EDS) analysis. The results proved a high dispersion of different Ag nanodomains onto MCM-41 and their chemical interaction with support and sulfur compounds by π-complexation. The best fit of kinetic and equilibrium data to pseudo-second order (R2 > 0.99) and Langmuir models (R2 > 0.98), respectively, demonstrate the occurrence of chemisorptive/catalytic interactions with organosulfur compounds, as seen in the XPS results. Its adsorption capacity (qm = 31.25 mgS/g) was 10 times higher than that obtained for pure MCM-41 and double the qm for Ag/MCM-41(C) adsorbent from commercial silica. The computational modeling approach provided valuable insight towards molecular level understanding of the mechanism in aromatic S-compounds adsorption over functionalized MCM-41 and the role of Ag species in this process.