| As the environmental standard is getting stricter, the limitation values of sulfur content in oil and oil products have kept decreasing worldwide. However, there exist many problems with the conventional petroleum desulfurizaiton technologies, such as complicated techniques, rigorous operation requirements and high investment. Especially, it is very difficult to remove low concentration thiophenes compounds in the oil. Therefore, it is necessary to develop a novel desulfurization technology.In the present study,γ-rays radiation method was put forward and investigated to convert thiophenes to any other compounds that were easily removed from the oil. Dodecane was used to simulate oil to study the radiated conversion of thiophene type compounds, and the kinetic model was studied.The results indicated that the gamma-rays radiation was effective to convert thiophenes compounds, and the conversion efficiency went up with the increase of the radiation dose. When the radiation dose rate was 3.8 kGy/h and the radiation dose was about 160 kGy, the conversion efficiency of benzothiophene (BT) and dibenzothiophene (DBT) was about 74% and 33%, respectively. At the same radiation dose, the conversion of DBT was higher at the lower initial DBT concentration or the higher radiation dose rate. The main conversion product of DBT was bisulfide, and oxygen in air showed slight inhibition to the conversion of DBT in the merely radiation system (without additives or catalysts).Tetrachloromethane displayed an improvement on the conversion efficiency of dimethyl thiophene and BT as a sensibilizer in the presence of gamma radiation at room temperature. The results also showed that the mixture of hydrogen preoxide and acetic acid appeared to be synergic with the radiation to convert DBT. When the ratio of oil: hydrogen preoxide: acetic acid was 3:1:1 and the radiation dose was about 200 kGy, the conversion efficiency of DBT was over 90%.The catalysts that could enhance the conversion of DBT in the simulated petroleum were selected. Among the tested catalysts, cobalt oxide and zirconium oxide impregnated onγ-alumina showed high catalytic activities under gamma-rays irradiation. The preparation conditions of the catalysts were also optimized experimentally. The main factors that affected the conversion of dibenzothiophene were studied. The results showed when the applied radiation dose rate was 3.9kGy and the radiation dose was about 179.2 kGy, the conversion efficiency of DBT was over 80% and 95% in the presence of cobalt oxide and zirconium oxide, respectively. The main conversion product of DBT was Dibenzo-sulfone.The effect of gamma-rays irradiation upon the structure of the catalyst was investigated by XRD, XPS and SEM techniques. The catalyst appeared to be stable under the gamma-rays irradiation except for the surface coverage by the oxidized organic compound. In addition, the possible mechanism for the synergistic effect of gamma-rays irradiation and catalyst was proposed.The first-order rate model could be used to well describe the conversion reaction kinetics of DBT. The reaction constant and G factor have been compared in different experiment condition. It is obvious that the reaction constant and G factor was higher when the catalysts were employed.According to the present study, the method by means of gamma-rays radiation to convert thiophene type compounds has been understood. The combination of the radiation with the catalyst has been proved to be an effective way to convert DBT to Dibenzo-sulfone, which could be easily removed from the oil. This study has provided a potential alternative to the deep petroleum desulfurization in the future.
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