Oxidative Desulfurization With Cumene Hydroperoxide Over Molybdenum Oxide-based Catalysts

As the environmental pollution caused by SOx which was produced along with the sulfur-contain oil combustion has become more and more severe, various countries have legislation to strictly limit the diesel oil of sulfur content. However, the conventional hydrodesulfurization (HDS) process is less effective for deep desulfurization, researchers have committed to develop new desulfurization process. Oxidative desulfurization (ODS) is drawing significant research interest because of its high desulfurization efficiency, low operating cost and simple technical process. This paper focuses on developing molybdenum oxide-based catalysts and exploring the mechanism of DBT oxidation with CHP over heterogeneous catalyst.In this paper, MoO3/SiO2supported catalysts were prepared by incipient wet impregnation method and modified by the introduction of Na, K and plasma. The catalysts were characterized by X-ray diffraction (XRD), ultraviolet-visible diffuse reflection spectrum (UV-vis), X-ray photoelectron spectrum (XPS), nitrogen adsorption isotherm method, inductively coupled plasma (ICP) and UV raman spectroscopy. The oxidative desulfurization performances were investigated in a fixed bed reactor using cumene hydroperoxide (CHP) as oxidant, and the toluene solution of dibenzothiophene (DBT) as the model fuel under mild conditions. The results indicated that the activity of modified catalysts was significantly improved, and the best atomic molar ratio of Na/Mo was0.2, while that for K/Mo was0.3. The catalyst modified by Na not only showed a high activity but a good stability. The conversion of DBT over the Na modified catalyst was still about95%after reacting for6h. Although the initial activity of the catalyst modified by K and plasma were high, but it decreased rapidly afterwards. The characterization results showed the introduction of Na could promote the dispersion of MoO3, the introduction of Na and K could promote the formation of Mo5+species, which could enhance the catalyst performance,whlie catalysts modified by plasma could promote the formation of oxygen vacancy. The introduction of K could destroy the structure of MoO3and form new species which could reduce the activity of catatyst.In addition, isopropyl alcohol and benzoquinone(BQ) were induced as free radical scavengers to explore the radical reaction mechanism. Combined with fluorescence spectrum characterization, the results showed that the mechanism of DBT oxidation with CHP over heterogeneous catalyst is hydroxyl free radical mechanism.What’s more, the bulk Ti-MoO2was prepared by solvothermal method and it was mechanical mixed with SiO2as an active component. The experimental results showed that Ti-MoO2is a highly efficient oxidation desulfurization activity component.