Keggin-Type POMs Immobilized on Fe3O4@SiO2 as Efficient Catalysts for Oxidative Desulfurization: Experimental and Monte Carlo Studies

Abstract

In this study, a novel phosphomolybdic Keggin-type polyoxometalate immobilized on silica-coated Fe₃O₄ nanoparticles (designated as FS/PMo) with a core–shell architecture was synthesized and characterized using XRD, FTIR, TEM, EDX, and VSM techniques. The catalyst demonstrated high efficiency in the oxidative desulfurization (ODS) of dibenzothiophene (DBT) using hydrogen peroxide as the oxidant. Key reaction parameters, including catalyst dosage, reaction temperature, and the molar ratio of H₂O₂ to DBT, were systematically optimized. Under optimal conditions, a sulfur removal efficiency of up to 99.53% was achieved. Owing to its magnetic core, the FS/PMo catalyst could be easily separated from the reaction medium using an external magnetic field and reused with minimal loss in activity. A plausible mechanism for the catalytic oxidation of DBT to its sulfone derivative (DBTO₂) was proposed. Furthermore, Monte Carlo simulations coupled with simulated annealing were employed to model the adsorption behavior of DBT on the FS/PMo nanocomposite, supporting the experimental findings and providing molecular-level insights into the ODS process.