Controllable Construction Of Iron-based Porous Ionic Liquid And Their Application In Extraction Desulfurization Of Fuel

Fuel is one of the primary energy sources globally,extensively utilized in various domains including transportation and industrial production.However,the combustion of fuel releases sulfur oxides（SO_x）,which may trigger acid rain and haze.Therefore,the removal of sulfides from fuel has emerged as a critical research topic.Recently,extraction desulfurization（EDS）has drawn increasing attention due to its advantages of mild reaction conditions,simple operation,economic,and environmental benefits.However,designing an efficient extractant is one of the key factors of the EDS process.Ionic liquids（ILs）exhibit potential applications in the fields of chemistry,materials,and energy due to their unique advantages,such as low volatility,high thermal stability,and wide electrochemical window.Iron-based ILs,a kind of Lewis acidic extractant,have exhibited important advantages over other materials owing to low viscosity,easy recovery,and simple synthesis.The Lewis acid-base interaction involved Fe³⁺could formπ-complexation bonding with aromatic sulfur compounds and thus enhanced the removal of sulfur species by iron-based ILs.However,the low single extraction efficiency and poor cycle stability limit the application of iron-based ILs.Therefore,many researchers have designed efficient extractants by optimizing the structure of ILs.Porous ionic liquids（PILs）as a novel class of liquid materials that combine the properties of ILs and solid porous materials.Compared with traditional ILs,PILs possess many unique advantages of ILs,such as good stability and recyclability.More importantly,the use of porous materials not only disperses extraction sites but also improves the mass transfer in the EDS systems.The use of PILs compensates for the drawbacks of conventional ILs,namely their poor recyclability and limited desulfurization performance.In this thesis,iron-based ILs were prepared by adjusting the ratio of anion and cation and the composition.The prepared iron-based ILs were employed as hindered solvents.Subsequently,a series of boron nitride-based PILs were synthesized by dispersing boron nitride into the iron-based ILs.The designed materials were used for the EDS systems.The main research conclusions of this thesis are listed as follows:（1）Iron-based quaternary ammonium ILs（Et₃NHCl/x Fe Cl₃,x=0.5,1.0,1.5,2.0）were synthesized by the one-pot method,and the EDS capacities were investigated.The results indicated that the extractive efficiency of Et₃NHCl/x Fe Cl₃for DBT increased with the molar ratio of Fe Cl₃/Et₃NHCl.The experimental conditions were as follows:T=50 ^oC,m _IL/m_oil=1:10,t=40 min.The extraction efficiency of DBT（dibenzothiophene）can approximately reach 100%under the above experimental conditions.The extraction capacities of different sulfur-containing substrates were studied,and the results showed that the sulfur removal rate could still reach 100%for4,6-dimethyldibenzothiophene（4,6-DMDBT）,4-methyldibenzothiophene（4-MDBT）,and benzothiophene（BT）.Additionally,the recovery of model fuel can reach up to98.9%,achieving the efficient recovery of clean fuel.（2）A pyridine-based PIL（x%-m-BN-PIL）was successfully prepared by using microporous boron nitride（m-BN）and N-butylpyridinium tetrachloroferrate（[BPy][Fe Cl₄]）as raw materials.The composition and chemical structure of the extractants were determined by X-ray diffraction,Fourier Transform infrared spectroscopy,UV-Vis absorption spectroscopy,X-ray photoelectron spectroscopy,and thermogravimetric analysis.It could be seen from that mainly interactions included hydrogen bonding and charge transfer between the m-BN and[BPy][Fe Cl₄].If[BPy][Fe Cl₄]is anchored on the interfaces of m-BN,it not only prevents porous material aggregation,but it further enhances extraction efficiency.The results confirmed that the EDS performance of x%-m-BN-PIL（x=1,3,5,7,15,20）was significantly superior to that of[BPy][Fe Cl₄]extractant under the experimental conditions of T=40 ^oC,t=60 min,m _IL/m_oil=1:5.Additionally,the desulfurization performance of the x%-m-BN-PIL was proportional to the amount of the m-BN.Under the optimal reaction conditions,the S-content of model fuel could be decreased from 450 ppm to 8 ppm via four stages of stepwise extraction.The recovery rate of model fuel can reach 98.6%.The desulfurization mechanism of the extractant was studied through characterization methods like Fourier Transform infrared spectroscopy and X-ray photoelectron spectroscopy.The results revealed that theπ-electron strengthening effect of m-BN on[BPy]⁺was the crucial factor in improving the extraction performance of the extractant.（3）A series of boron nitride-based bis-imidazole cationic PILs（x%-G-BN-PILs）were constructed by a one-pot synthetic method.The chemical structure and composition of extractants were analyzed by Fourier Transform infrared spectroscopy,Raman,proton nuclear magnetic resonance,nitrogen adsorption-desorption experiments,gas absorption experiments,and molecular simulation calculations.The results show that there is hydrogen bonding between G-BN and IL.7%-G-BN-IL is a low-viscosity liquid material with abundant porous structures.The reaction conditions were optimized as follows:T=30 ^oC、t=60 min、r=600 rpm.Under the above experimental conditions,the results indicated that 7%-G-BN-PIL is capable of extracting large quantities of sulfides when compared with[C₆BIm₂][Fe Cl₄]₂（+21.4%of DBT,+28%of 4-MDBT and+30%of 4,6-DMDBT）.Additionally,the removal rate of DBT can be about 100%after four-stages extraction,achieving the purpose of ultra-deep desulfurization.