Oxidative desulfurization of dibenzothiophene based on molecular oxygen and iron phthalocyanine

Direct oxidation of dibenzothiophene (DBT) based on molecular oxygen and iron tetranitrophthalocyanine (FePc(NO2)4) catalyst was performed in hydrocarbon solvent under water-free condition for deep desulfurization. Conversion of DBT in decalin reached 98.7 wt.% at 100 °C and 0.3 MPa of initial pressure with 1 wt.% of FePc(NO2)4 over the whole solution for 2 h. In addition to FePc(NO2)4, another two catalysts, FePc(NO2)3NH2 and FePc(NH2)4, were synthesized to investigate the effect of substituents of iron phthalocyanines on their catalytic activities. The results show that the catalytic activity of these phthalocyanines decreases in the order of FePc(NO2)4 > FePc(NO2)3NH2 > FePc(NH2)4, indicating that the electron-donating group has negative effect on the catalytic properties. Activity of FePc(NO2)4 was kept unchanged after 5 runs of oxidation; whereas, activity of FePc(NH2)4 decreased because of its decomposition. Moreover, FePc(NO2)3NH2 was supported on a polyacrylic cationic exchange resin and its activity was remarkably enhanced to the level of FePc(NO2)4. Oxidative desulfurization of a model fuel, 500 μg/g solution of DBT in decalin, was performed based on the catalytic oxidation using molecular oxygen and FePc(NO2)4 catalyst. The lowest sulfur content in the model fuel could be decreased to less than 4 μg/g after the treatment of this oxidation and a combined adsorption.