Combined Extraction-Oxidation System for Oxidative Desulfurization (ODS) of a Model Fuel

An efficient extractionoxidation catalytic system for deep desulfurization of a model fuel was explored. First, Mo/gamma-Al2O3 catalysts were prepared using an impregnation method and were characterized using X-ray diffraction, temperature-programmed reduction, and N-2 physical adsorption isotherms. Acetonitrile, methanol, N,N-dimethylformamide, N-methylpyrrolidone, and H2O were added to investigate the influences of different extracting agents for extractionoxidation desulfurization. Acetonitrile showed synergistic action for dibenzothiophene oxidation and a comparatively low dissolving capacity for aromatic compounds. Under a n(H2O2)/n(S) molar ratio of 2.3 and v(oil)/v(acetonitrile) of 3:1, benzothiophene, dibenzothiophene, and 4,6-dimethyldibenzothiophene were almost completely removed in the presence of the 16 wt % Mo/gamma-Al2O3 catalyst over 40 min at 333 K. A reaction pathway based on extractionoxidation was proposed in which the sulfur compounds were transferred to the extracting phase before oxidizing to form sulfones in the extracting phase. The extraction process was rapid relative to the oxidation process. The advantages of the extractionoxidation catalytic system are that a high sulfur removal can be achieved under a lower n(H2O2)/n(S) molar ratio and that the stability of the catalyst is significantly improved.