Synthesis Of Multifunctional FeCl₃-Based Ionic Liquids And Their Catalytic Oxidation Desulfurization Of Fuel Oils

The combustion of sulfur-containing compounds in gasoline,diesel and other fuel oils is one of the main factor causing environmental pollution including acid rain,haze and fine particulate matter?PM 2.5?.In recent decades,extraction or/and oxidation desulfurization routes have been developed because of their easy-operation,low-cost and high efficiency,which are ideal complementary techniques to desulfurize the after-HDS-treated oils.In this work,N-methyl-2-pyrrolidonium?NMP?is acidized by hydrochloric acid to form[Hnmp]Cl and then reacted with FeCl₃ to obtain a series of inexpensive[Hnmp]·xFe Cl₄?x=0.2-2.0?ionic liquid?ILs?for extraction/oxidation desulfurization of model oils.The Lewis acidity of the ILs are characterized by Fourier transform infrared?FT-IR?test,which indicates that when x value in[Hnmp]·xFeCl₄ is above is above 1.0,the ILs would exhibit Lewis acidity.The extraction results show that the acidification for NMP reduces its dissolubility ability toward dibenzothiophene?DBT?and Lewis acidity plays determining role for extraction desulfurization.DBT and thiophene can be almost totally removed by[Hnmp]·1.5FeCl₄ and[Hnmp]·2.0FeCl₄ in 30 min and 5 h,respectively,even at the high ratio of V?oil?/V?IL?=10,showingtheastonishingdesulfurizationabilityoftheseinexpensiveILs.In extraction/oxidation removal process of DBT model oil,scavenger experiments and electron paramagnetic resonance?EPR?tests show that both hydroxyl radical?·OH?and superoxide anion radical?^·O₂^-?are generated from H₂O₂,while·OH plays key role and and·O₂^-has minor function.The[Hnmp]·1.0FeCl₄ IL shows excellent recycling performance,which can be attibuted to its high solubility?23700 ppm?for dibenzothiophene-sulfone?DBTO₂?.Basedontheexcellentextraction/oxidativedesulfurizationdegreeof[Hnmp]·1.5FeCl₄ ionic liquids for DBT,we studied the synthesis of supported ionic liquids and their phase transfer catalytic oxidation desulfurization performance.The[Hnmp]·1.5FeCl₄ was successfully immobilized on the?-Al₂O₃ which prepared by hydrothermal method and solution combustion method,respectively.Serials of charization methods,FT-IR,XPS,and EDS indicate that the ionic liquid was successfully supported onto alumina.Molecular simulations and BET analysis showed that[Hnmp]·1.5FeCl₄/hydrothermal Al₂O₃ exposed more active sites of model oil.Using the catalyst to the phase transfer catalytic oxidation desulfurization experiment and determine the optimal experiment conditions.When the model oil with 200?g/g sulfur content is 10 mL,1.0 g catalyst is used as the optimal catalyst dosage,n?H₂O₂?/n?S?=16 is selected as the optimal oxygen-sulfur ratio of the reaction system,and 5mmol of TBAB is selected as the best amount of phase transfer catalyst.