Continuous Extraction-oxidation Coupling Process For Deep-desulfurization Of Fuels

In this work,model fuels with a sulfur content of 320 ppmw were prepared by dissolving BT,DBT or 4,6-DMDBT into n-octane,respectively.The experiments of sulfur removal for model fuels and diesel fuel,either by sole extraction and by sole oxidaton or by simultaneous extraction-oxidation were performed in a batch reactor at different temperatures.Finally,a continuous extraction-oxidation desulfurization system was established.The Mo/?-Al2O3 catalyst was prepared by incipient wetness impregnation of ?-Al2O3 with an aqueous solution of(NH4)6Mo7O24·4H2O at different calcination temperatures.The Mo/?-Al2O3 catalyst before and after the treatment by H2O2 was characterized by XRD,XPS,FT-IR and Raman spectra.The results revealed that Al2(MoO4)3 on surface support is the active component of the Mo/?-Al2O3 catalyst.Moreover,the crystal type of Al2(MoO4)3 calcined at 700? begins to chang and make the catalyst deactivation.Meanwhile,the proposed mechanism of DBT oxidated by Mo/?-Al2O3 catalyst was acquired:The active peroxomolybdate species(abbreviated as Mo(O2))are formed,where Mo=O group interacts with H2O2 to undergo a loss of a water molecule on the alumina surface;the sulfoxide is formed by the nucleophilic attack of DBT on Mo(O)2 to form sulfoxide and Mo=O;subsequently,the sulfoxide undergoes further oxidation by a peroxide oxygen of the molybdenum peroxo specie to form sulfone.Different solvents were added to investigate the effect of different extractants in the extraction-oxidation desulfurization process,respectively.The results revealed that sulfolane,PEG-400 and acetonitrile were added to the extraction-oxidation desulfurization system and made the extraction process and the catalytic oxidation reaction express synergistic action of desulfurization.The effects of different hydrocarbon components on DBT removal were studied.The addition of different hydrocarbon components had no effect on the removal of DBT in mode fuels.Simultaneously,the intersolubility of n-octane and the extractant,such as sulfolane,PEG-400 and acetonitrile was measured and also the removl rate of the other hydrocarbon components in model fuels was determined.In order to study the heterogeneous liquid-liquid-solid system,the reactivity on each phase was individually assessed.A kinetic model of the EODS process for dibenzothiophene in the model fuel was developed,comprising the chemical kinetic mechanism and mass transfer effects.The kinetic parameters of the kinetic model such as the kinetic constants and apparent activation energy were determined.The EODS system in the experimental condition is co-controlled by mass transfer and chemical reaction,as the terms involving the intrinsic resistance of the chemical reaction are no more important than mass transfer resistance.A continuous flow system of the extraction-oxidation desulfurization of model fuels and diesel fuel with H2O2 as oxidant,PEG-400 as extractant and Mo/?-Al2O3 as catalyst was performed in the extraction-desulfurization device at 60?.