Deep oxidative desulfurization via rGO-immobilized tin oxide nanocatalyst: Experimental and theoretical perspectives

In this contribution, reduced grapheme oxides (rGO) with immobilized tin oxide (SnO2) nanocatalysts were synthesized via the Incipient Wetness Impregnation (IWI) method. To characterize the SnO2/rGO composites, several analyses including the; XRD, Raman, FTIR, ICP-OES, BET-BJH, XPS, TEM, and TPD were utilized. Then the effects of parameters including reaction time, total metal loading, and the initial sulfur concentration of model fuel in the dibenzothiophene (DBT) oxidation desulfurization process were evaluated. After determining the optimal conditions for the aforementioned parameters, the influences of 3 effective factors of the molar ratio of oxidant/substrate (O/S), the molar ratio of catalyst/substrate (Cat/S), and reaction temperature were investigated by applying response surface methodology (RSM). Results revealed that through employing the SnO2 (15)/rGO catalyst, the DBT conversion of 96% was obtained at the following optimum conditions: time = 180 min, initial sulfur concentration = 500 ppm, molar ratio of O/S = 30, temperature = 60 °C and molar ratio of Cat/S = 0.06. Next, 1H NMR and FTIR techniques were performed for the final product assessment. Ultimately, to investigate the importance of the rGO upon the DBT oxidation, density functional theory (DFT) calculations were utilized. Interaction energy, Reactivity parameters, ESP, and RDG results revealed the influence of the rGO in the adsorption of the DBT through the π–π interactions.