Effect of calcium and iron doping over MoO3-PO4/Al2O3 catalyst in oxidative desulfurization of Malaysian diesel

Abstract

The catalytic oxidative desulfurization (Cat-ODS) process has emerged as a new technology to achieve ultra-low sulfur levels in diesel fuels. The effect of calcium and iron dopant in MoO3-PO4/Al2O3 catalyst were tested on desulfurization reaction at ambient condition. The oxidizing reagent used was tert-butyl hydroperoxide (TBHP) and dimethylformamide (DMF) acted as an extraction solvent. A commercial Petronas diesel with 440 ppmw of total sulfur was employed to evaluate the elimination of sulfur compounds. The result obtained revealed that Fe/MoO3-PO4/Al2O3 catalyst gave superior performance towards desulfurization. The Fe/MoO3-PO4 catalyst was able to reduce the sulfur in commercial diesel from 440 to 79 ppmw with 82% of total sulfur removal while Ca/MoO3-PO4/Al2O3 catalyst only achieved 76% of sulfur removal. Ammonia temperature programme desorption (TPD) analyses showed that the Fe/MoO3-PO4/Al2O3 catalyst contained both strong and weak acid sites while field emission scanning electron microscopy (FESEM) micrograph illustrated well-dispersed homogeneous structure. The mechanistic study showed that it was depended on the type of dopant as the Fe/MoO3-PO4/Al2O3 catalyst tended to form sulfone in the oxidative desulfurization reaction meanwhile, the sulfoxide formation was dominated in the oxidative desulfurization reaction using Ca/MoO3-PO4(10:90)/ Al2O3 catalyst. The results obtained showed that Fe/MoO3-PO4(10:90)/Al2O3 catalyst can be used as a potential catalyst for the removal of sulfur in Malaysian diesel to achieve Euro IV diesel.