A novel method for oxidative desulfurization of liquid hydrocarbon fuels based on catalytic oxidation using molecular oxygen coupled with selective adsorption

The present study explored a novel oxidative desulfurization (ODS) method of liquid hydrocarbon fuels, which combines a catalytic oxidation step of the sulfur compounds directly in the presence of molecular oxygen and an adsorption step of the oxidation-treated fuel over activated carbon. The ODS of a model jet fuel and a real jet fuel (JP-8) was conducted in a batch system at ambient conditions. It was found that the oxidation in the presence of molecular oxygen with Fe(III) salts was able to convert the thiophenic compounds in the fuel to the corresponding sulfone and/or sulfoxide compounds at 25 °C. The oxidation reactivity of the sulfur compounds decreases in the order of 2-methylbenzothiophene > 5-methylbenzothiophene > benzothiophene ≫ dibenzothiophene. The alkyl benzothiophenes with more alkyl substituents have higher oxidation reactivity. In real JP-8 fuel, 2,3-dimethylbenzothiophene was found to be the most refractory sulfur compound to be oxidized. The catalytic oxidation of the sulfur compounds to form the corresponding sulfones and/or sulfoxides improved significantly the adsorptivity of the sulfur compounds on activated carbon, because the activated carbon has higher adsorptive affinity for the sulfones and sulfoxides than thiophenic compounds due to the higher polarity of the former. The remarkable advantages of the developed ODS method are that the ODS can be run in the presence of O2 at ambient condition without using peroxides and aqueous solvent and thus without involving the biphasic oil–aqueous-solution system.