Deep Desulfurization Of Diesel By Catalytic Oxidation With Functionalized Deep Eutectic Solvent

A new generation of green solvent,deep eutectic solvents?DESs?,as a catalyst and extractant,are now of receiving increasing interest in the fields of organic synthesis,electrochemistry and catalysis.In this study,a series of acetamide-based acidic eutectic mixtures were synthesized with different molar ratios of acetamide and glutaric acid,and applied to extraction and catalytic oxidative desulfurization?ECODS?.The results indicate that the composition of DESs is related to oxidative desulfurization activity.Under optimal conditions,the desulfurization efficiencies of acetamide/glutaric acid?molar ratio1:2?DES can reach up to 99%in 3 h.In addition,it was speculated by FT-IR and ¹HNMR that DES formed hydrogen bonds.Finally,the DES was successfully applied for the deep oxidation desulfurization of 1#real fuels.Although the broad application prospect of DES,the study of DESs does not involve aerobic oxidation desulfurization?AODS?so far and further research is intensely craved.H₂O₂ or O₂ which are green and environmental friendly has been widely used in oxidation reactions.However,it is difficult to activate dioxygen under mild conditions due to the high activation barrier.Therefore,in this work,a unique coupled redox catalysis biomimetic approach system using an Anderson-type polyoxometallates?POM?,?NH₄?₃Co?OH?₆Mo₆O₁₈ and p-Toluenesulfonic acid?p-TsOH?-based deep eutectic solvents?DESs?as cocatalysts,which performed as electron donor and electron-transfer mediator?ETMs?,exhibits excellent desulfurization performance and can selectively oxidize the sulfides in diesel into their corresponding sulfones under mild conditions in absence of any sacrificial agent.The removal of DBT can reach 99%at 60 ^oC in 1 h.A possible mechanism combining with the results of the UV-vis was proposed,the use of coupled redox systems with ETMs facilitates the reaction process by transporting the electrons from Co-POM to the oxidant along a low-energy pathway and finally DBT was prone to oxidize to DBTO₂.Owing to the advantages of cheap and biodegradable raw materials,high desulfurization efficiency without any sacrificial agents under mild conditions and high recyclability,the biomimetic approach provides a novel and green practical method with low-cost and high-performance for deep desulfurization of diesel.A series of polyethylene glycol based deep eutectics solvents are synthesized btwteen PEG2000 and six different kinds of organic acids including 5-sulfosalicylic acid?SSA?,salicylic acid?SA?,p-aminosalicylic acid?PAS?,3,4-Dihydroxybenzoic acid?3,4-DHBA?,oxalic acid dihydrate?OXA?and DL-malic acid?DL-MA?.These DESs coupled with the newly prepared chromium polyanions catalyst are employed for oxidative desulfurization reactions.Among them,the removal of DBT reached as high as 99%with 5-sulfosalicylic acid/polyethylene glycol 2000?SSA/PEG2000?DES at 60 ^oC in 2 h,which is much higher than the desulfurization efficiency of the other five DESs.Moreover,it is proved that the physical properties of DESs such as conductivity and viscosity are related to their composition.SSA/PEG2000 DES with higher conductivity and lower viscosity usually facilitates the oxidative desulfurization reaction.The Na₃H₆CrMo₆O₂₄ catalyst was characterized by FT-IR,UV-vis,XRD and XPS.Therefore,the Anderson-type structure of the chromium polyanions catalyst was demonstrated.Finally,the system was successfully applied for the desulfurization process of 1#and 2#Diesel,respectively.The sulfur content of the 1#diesel was reduced from 24 ppm to 4 ppm,achieving deep catalytic oxidative desulfurization.The sulfur level of 2#diesel can be decreased from 242 ppm to21 ppm,and the conversion rate was 91%.