Study On Desulfurization Of Oil Catalyzed Oxidation By Supported Heteropoly Acid In Microemulsion

Deep desulfurization of diesel has become an important research subject due to the increasing regulations of reducing sulfur content in most countries. At present, the main adopted way to reduce sulfur content in diesel is hydrodesulfurization (HDS) and non-hydrodesulfurization, hydrodesulfurization (HDS) can effectively remove the majority of sulfur-containing compounds in diesel, but it is difficult to remove DBT and its derivatives. Therefore, the world is devoted to the development of new technologies, among them, Oxidative desulfurization is considered to be one of the most promising desulfurization methods for its mild reaction condition and high efficiency.In this study, the lignite semi-coke from Ordos Inner Mongolia is selected as carrier to prepare catalysts, phosphotungstic acid /semi-coke, phosphotungstic acid supported on semi-coke with various phosphotungstic acid loading, are prepared by impregnation, In addition, BET,FTIR,NH3-TPD,XRD,SEM and TG-DTA are employed to analyze the surface area, pore structure, functional groups, acid intensity, crystal structure and thermal stability of the supported phosphotungstic acid catalyst. With phosphotungstic acid /semi-coke as catalyst, 30%hydrogen peroxide as oxidant and span60 as surfactant, organic sulfur compounds are removed from FCC diesel by a catalytic oxidation method. The effect of reaction temperature, reaction time, the amount of catalyst, the amount of span60 and the amount of hydrogen peroxide on desulfurization are investigated. The quantification of sulfur in the reaction products are conducted by microcoulometry analysis (WD-2K), the sulfur compounds in the original liquid fuels and the desulfurized are analyzed by GC-950. The oxidative desulfurization of FCC diesel is also explored in the continuous operation conditions. At last, the oxidation process conditions of DBT are optimized, reaction kinetics of oxidation of DBT and FCC diesel are studied.The results of characterization show that the Keggin structure of catalysts remains unchanged, Phosphotungstic acid disperse on the support or into the inner hole in the form of micro-crystalline cluster, the acid strength of catalysts increases a little when the increase of loading, catalysts show good thermal stability. Oxidative desulfurization on the FCC diesel is conducted. The result shows that the order of the influence factors for the sulfur removal efficiency is: the amount of hydrogen peroxide> the amount of HPW/Sc2 > reaction time > reaction temperature> the amount of Span60, the optimum reaction conditions are as follows: reaction temperature at 60℃, reaction time 60min, 1wt% of HPW/Sc2, [H₂O₂]/[S]=3, 0.36wt% of Span60.Sulfur compounds in oxidized FCC diesel are removed by extraction, the NMP of 90%used as extraction agent, the three important factors, extraction time, extraction temperature and the volume ratio of extraction agent to FCC diesel are investigated, the best extraction condition is: the volume ratio of extraction agent to FCC diesel is 1:1, extraction time 10min, extraction temperature 25℃, the sulfur removal efficiency and the yield of the oil are 79.83% and 98.0%, sulfur compounds in oxidized FCC diesel are removed by adsorption, CuO is selected as adsorbent, the sulfur removal efficiency can come up to 86.03%.The result of model compounds experiment indicates that aromatic hydrocarbon, olefins and nitrogen compounds have influence on the removal of model compounds, and the sequence of them influence from big to small is quinoline, cyclohexene, benzene; the oxidation reactivities of model compounds decrease in the order of DBT>4,6-DMDBT>BT. The oxidation reaction of DBT and FCC diesel fits well with pseudo-first-order reaction kinetics.The fresh and regenerated HPW/Sc2 catalyst are characterized by means of SEM, FT-IR and UV-Vis DRS. The results show that FT-IR spectra and UV-Vis DRS spectra of fresh and regenerated catalysts are almost the same, and the catalyst maintains the structure of Keggin. The regenerated catalyst demonstrates the same catalytic activity as the fresh catalyst; the used extractants are recycled by distillation. The sulfur removal efficiency is reduced by 6.5% with recycled NMP.