Green Oxidative Desulfurization(ODS) Of Diesel

In this paper,a series of L-proline-based DESs was prepared through an atom economic reaction between L-proline?L-Pro?and four different kinds of organic acids.The DESs were characterized by Fourier transform infrared spectroscopy?FT-IR?,H nuclear magnetic resonance?¹HNMR?,cyclic voltammogram?CV?and the Hammett method.The synthesized DESs were used for the oxidative desulfurization and the L-Pro/p-toluenesultonic acid?L-Pro/p-TsOH?system shows the highest catalytic activity that the removal of dibenzothiophene?DBT?reached 99%at 60?C in 2 h,which may involve the dual activation of the L-Pro/p-TsOH.The acidity of four different L-proline-based DESs was measured and the results show that it could not simply conclude that the correlation between the acidity of DESs and desulfurization capability was positive or negative.The electrochemical measurements evidences and recycling experiment indicate a good stability performance of L-Pro/p-TsOH in desulfurization.Despite the significance of hydrogen bonds in DESs in desulfurization reaction,little is understood about the relationship between the DES components,hydrogen-bond strengths and oxidative desulfurization activity.In the second study a class of caprolactam-based acidic DESs was prepared with different molar ratio of caprolactam?CPL?and oxalic acid?OXA?.The prepared DESs were characterized by differential scanning calorimetry?DSC?,FT-IR,¹HNMR and thermo-gravimetric analyses?TGA?.These DESs were employed for the ODS and the desulfurization efficiency changes regularly with the the variation in compositions of DESs.The influencing factors on the removal of DBT were systematically investigated and the desulfurization efficiency of the caprolactam-based acidic DESs can reach as high as 98%under optimal conditions.The removal of different sulfur compound was in the sequence of DBT>4,6-dimethyldibenzothiophene?4,6-DMDBT?>benzothiophene?BT?.Combined with experimental data and characterization results,it was found that the oxidative desulfurization efficiency of the system could be affected by the interaction of hydrogen bonds,which could be changed by means of adjusting the composition of DESs.The finding of hydrogen bonds in DESs provides a new insight in the understanding of deep desulfurization mechanism of diesel.In the third study,the aim is to explore a catalytic oxidative desulfurization of model and actual oil under mild reaction conditions.A novel POM-based ionic liquids,[3-?pyridine-1-ium-1-yl?propane-1-sulfonate]₃?NH₄?₃Mo₇O₂₄·4H₂O,abbreviated[PyPS]₃?NH₄?₃Mo₇O₂₄,was synthesized and employed as a catalyst with high activity and selectivity in the ODS.The[PyPS]₃?NH₄?₃Mo₇O₂₄ catalyst showed highly activity in oxidative desulfurization system that the DBT remove 99%could be obtained under quite mild conditions(T=25 ^oC,n?catalyst?=0.0056 mmol,t=60min,n?H₂O₂?/n?sulfur?=3,V_IL/V_{Model Oil}=1/10).Characterization of the catalyst by XRD,FT-IR,TG-DTA and X-ray photoelectron spectroscopy?XPS?was conducted to confirm its structure.Some important parameters which affect the ODS process,such as temperature,hydrogen peroxide dosage reaction systems and different sulfur compounds,were systematically studied.The effect of the concetration of aromatics?toluene and naphthaline?on this oxidative desulfurization system was also investigated.This catalytic oxidative desulfurization system could recycle five times without a significant decrease in the catalyst activity.Furthermore,the sulfur level of the actual diesel can be reduced from 242 to about 10 ppm after desulfurization reaction under optimum conditions.