This work presents the results obtained in the development of phosphotungstic acid/semi-coke catalysts in the oxidative desulfurization (ODS) process of diesel fuel using hydrogen peroxide as the oxidizing agent, N-methyl-2-pyrrolidone(NMP) and water as as extractive solvent,span-60 as surfactant. Phosphotungstic acid /semi-coke prepared by impregnation, was characterized by X-ray diffraction. The effects of the amount of catalyst, surfactant.and oxidation agent used, two phase volume ratio, reaction temperature and reaction time, on the efficiency of desulfurization were investigated. The results showed that the activity for sulfur elimination depends mainly on reaction temperature and two phase volume ratio.The experimental results indicated that the optimum process conditions were as followed; the amount of oxidant was 2.5% of the volume of diesel,the amount of catalyst was 0.08g in 20ml diesel,the reaction temperature 30ºC.the reaction time 60 min.At this operation condition, the sulfur level of the desulfurized diesel can be lowered from about 1300 ppm to below 50 ppm after oxidation and extraction ,96% of the sulfur could be removed from the diesel oil. Phosphotungstic acid /semi-coke catalyst can be used repeatedly.
In addtion. the diesel after oxidation and extraction was analyzed by GC-FPD for sulfur content. The chromatograph shows that virtually all the sulfur containing compounds in diesel were removed. The result may indicate that this oxidative desulfurization system has a potential to meet future regulations of sulfur in diesel fuels.