Preparation And Oxidative Desulfurization Performance Of Magnetic Composite Materials

With the rapid increase of the national economy, the rapid development of the industry and manufacturing industry makes us increasing demand for fuel oil, the presence of sulfur compounds may cause serious environment pollution, so it is stringent to control sulfur content of fuel oil. The conventional hydrodesulfurization technology can’t meet the requirement of deep desulfurization. In recent years, the oxidative desulfurization technology attracts much attention because of its mild reaction conditions, and high desulfurization rate. The metal oxide catalysts used in oxidative desulfurization are not easy to be separated from the oil, which restricts their practical application. Therefore, in this thesis, the magnetic oxides were prepared and applied in oxidative desulfurization of dibenzothiophene model oil.1. The magnetic Fe3O4/MoO3 composite catalysts were synthesized by precipitation method, with ammonium molybdate as raw materials, n-octane as model oil, tert-butyl hydroperoxide (TBHP) as oxidant, dibenzothiophene (DBT) as analog sulfide, and investigated the effects of magnetic oxide oxidative desulfurization of the model oil. The morphology and structure of Fe3O4/MoO3 were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscope (SEM), and the surface valence states of the catalyst were analyzed by X-ray photoelectron spectroscopy (XPS), as well oxidative desulfurization reaction product was speculated by infrared spectroscopy. The effect of the reaction time, catalyst amount, reaction temperature and the amount of the oxidant were investigated on the catalytic performance in the removal of dibenzothiophene. The results show that the optimal reaction conditions are as follows:the amount of catalyst, O/S, the temperature and time were 6 mg,4:1,90 ℃ and 3 h, respectively. Under this optimal condition, the obtained desulfurization rate of model oil can reach 99.5%. The absorption bands for sulfone at 1288 cm’1,1166 cm-1and the absorption band for sulfoxide at 1047 cm-1 were detected in the IR spectrum, indicating that DBT was oxidized to DBTO and DBTO2 over Fe3O4/MoO3 catalyst. The sulfide oxidizing activity is in the sequence of dibenzothiophene> benzothiophene> thiophene. The cycles experiments indicate the stability of the magnetic catalyst.2. The magnetic Fe3O4/WO3 catalysts were synthesized by using grind-calcination method. The structure of the catalysts was analyzed by XRD and SEM. Meanwhile, the catalytic oxidation desulfurization performance of DBT was studied. The results show that Fe3O4/WO3 catalyst has high catalytic activity. When the loading amount of WO3 is 35%, the reaction temperature is 100℃, the amount of catalyst is 10 mg, the O/S molar ratio is 12:1, and the reaction time is 4.5 h, the removal rate of DBT was 94.2%. After recycling six times, the desulfurization rate of Fe3O4/WO3 catalyst reduced to 84.6%. Compared with Fe3O4/WO3, Fe3O4/MoO3 exhibits higher catalytic activity and stability.