Merging experimental and theoretical approaches towards understanding real diesel fuel desulfurization by nanoporous carbons

Experimental tests combined with theoretical calculations have yielded new insights into real diesel fuel desulfurization (rDeSulfur) using activated nanoporous carbons. The carbons were selected for their varying physicochemical properties and further were chemically treated to modify their surface chemistry, aiming to investigate the impact of the major physicochemical features on rDeSulfur. The experimental findings demonstrated that both porosity and surface chemistry play complex roles. Specifically, a high degree of graphitization and diverse pore size distributions enhanced adsorptive capabilities, with some carbon samples achieving ultra-deep desulfurization levels (<1 ppmwS). Theoretical calculations indicated that π-π stacking through dispersion forces was the primary mechanism of adsorption. While surface functionalities at the edges of graphene had minimal impact on interaction strength, structural defects, especially clusters of three quaternary nitrogen atoms or single defected vacancy with OH group, improved interaction energies, boosting adsorption effectiveness compared to pristine graphene. The study concludes that the effectiveness of carbons in diesel desulfurization depends heavily on graphitization levels, defects, and where specific functionalities are located. Lastly, although aromatic compounds in diesel, like benzene, toluene, and naphthalene, compete with thiophenics for adsorption, they have lower interaction energies, suggesting preferential adsorption of sulfur compounds over the aromatics.