A new phase transfer nanocatalyst NiFe2O4-PEG for removal of dibenzothiophene by an ultrasound assisted oxidative process: kinetics, thermodynamic study and experimental design

In this study, NiFe2O4-PEG, an effective nanocatalyst was synthesized via a hydrothermal method using different PEG concentrations and synthesis times. The synthesized nanocatalyst was used in the ultrasound assisted oxidative desulfurization (UAOD) of model fuels (e.g. n-hexane and dibenzothiophene (DBT)) for the first time. The nanocatalyst was then characterized by XRD, FTIR, BET, SEM, VSM and TEM analyses. In addition, central composite design was used to evaluate the effective variables on the UAOD process. The optimal values of effective factors such as catalyst dose, oxidant amount, irradiation time and ultrasonic power to maximize of the percentage of sulfur removal were 0.149 g, 15 mL, 11.96 min, and 70 MHz, respectively. Moreover, the kinetic aspects of the oxidation reaction of DBT in the UAOD process were investigated using a pseudo-first-order model. Furthermore, using the Arrhenius equation, an activation energy of 35.86 kJ mol(-1) was obtained. Additionally, thermodynamic analysis showed that the oxidation reaction of DBT was endothermic with a positive Gibbs free of energy, indicating the non-spontaneity of oxidation of DBT in the UAOD process. Moreover, the conversion rate of DBT has increased from 57% at 35 degrees C to 85% at 65 degrees C.