Oxidative desulfurization using nanocomposites of heterogeneous phosphotungstic acid over natural zeolites; optimization by central-composite design

Abstract In this research, the phosphotungstic acid (PTA) was impregnated on natural zeolites of clinoptilolite (Clin), mordenite (Mord), ferrierite (Ferr), and natrolite (Nat) and was characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX. The synthesized heterogeneous nanocomposites were used for oxidative desulfurization of dibenzothiophene (DBT). Among samples, PTA-Ferr has removed the most amount of DBT (82.02%) from model fuel and PTA-Nat, PTA-Clin, and PTA-Mord indicated 56.00%, 73.62%, and 67.05% removal of initial DBT, respectively. PTA-Ferr had a high surface area of 293.6 m2/g, agglomeration-free particles with an average size of 10.2 nm. To study the effect of operating parameters such as reaction time, reaction temperature and DBT concentration on the ODS activity of PTA-Ferr, a central composite design (CCD) was used. Optimized conditions for the highest DBT removal (94.39%) were obtained at a reaction time of 55 min, the temperature of 60 °C and a DBT concentration of 250 ppm.