Photocatalytic oxidative desulfurization of dibenzothiophene under simulated sunlight irradiation with mixed-phase Fe2O3 prepared by solution combustion

Abstract

Mixed-phase Fe₂O₃ was prepared from Fe(NO₃)₃ and (C₂H₅)₃NHCl via solution combustion. Photocatalytic oxidative desulfurization of dibenzothiophene (DBT) under simulated sunlight irradiation using mixed-phases of α- and β-Fe₂O₃ as catalysts was investigated. The DBT in the oil phase was extracted into water phase and then photooxidized to CO₂ and SO₄²⁻ by Fe₂O₃ and O₂ dissolved in water. The Fe₂O₃ containing 36.6% β-Fe₂O₃ and 63.4% α-Fe₂O₃ exhibited the highest photocatalytic activity. Sulfur removal of DBT in n-octane was 92.3% for 90 min irradiation under the conditions of V(water) : V(n-octane) = 1 : 1, air flow rate at 150 mL min⁻¹, and Fe₂O₃ addition at 0.05 g. The kinetics of photooxidative desulfurization of DBT was a pseudo-first-order with an apparent rate constant of 0.0287 min⁻¹ and half-time of 24.15 min. The sulfur content of the actual diesel could be reduced from 478 μg mL⁻¹ to 44.5 μg mL⁻¹ after 90 min. The radical scavengers experiments and terephthalic acid fluorescence technique indicated that ˙OH and O₂˙⁻ were the main reactive species in the DBT photocatalytic degradation. A potential photocatalytic desulfurization mechanism using mixed-phase Fe₂O₃ was proposed.