Synthesis Of Phosphotungstic Acid Based Ionic Liquid Catalyst And Study On Extraction Coupled Photocatalytic Oxidative Deep Desulfurization In Diesel

With the steady growth of the global population and the vigorous development of social economy,human demand for energy supplies has been unprecedentedly high,especially for fuel oil.However,the waste SO_x produced by the combustion of fuel oil has brought severe industrial and environmental challenges to human society.Desulfurization of fuel oil is of great significance for producing clean energy because of the increasingly stringent environmental regulations.Photocatalytic oxidative desulfurization is considered to be one of the most promising desulfurization technologies due to its advantages of no hydrogen consumption,environmental friendliness and low operating cost.The research content of this paper is centered on the phosphotungstic acid based ionic liquid catalyst,designing and establishing a conventional ionic liquid or deep eutectic solvent as the extractant,using the synergistic effect of extraction and photocatalytic oxidation to achieve the deep removal of sulfur-containing compounds in model diesel oil.Finally,the possible reaction path and mechanism were studied and speculated.The main contents of this work are as follows:(1)The quaternary phosphine-phosphotungstic acid based ionic liquid was prepared as catalyst,and the cheap and non-toxic choline chloride-based deep eutectic solvent was prepared as extractant.The subsequent activity experiments explored the performance of catalyst for the removal of sulfur-containing compounds in low-sulfur model oil under UV irradiation.Through the elemental analysis,FT-IR,XRD,TG,XPS and other characterization methods to analyze the structure of the prepared catalyst and extractant.The photocatalytic activity experiment results showed that the removal ratio of DBT is up to 96.5%for low sulfur concentration of 20 ppm under condition which were 0.05 g of catalyst,3 m L of deep eutectic solvent,200?L of isobutyraldehyde,air flow of 300 m L/min and UV irradiation time 90 min.In addition to other sulfur compounds(4-methyldibenzothiophene(4-MDBT)and4,6-dimethyldibenzothiophene(4,6-DMDBT))can also show excellent desulfurization performance.ESR and free radical scavenging experiments showed that there were many active substances in the photocatalytic system under UV irradiation.Further more,GC-MS analysis of the products of the extraction coupled photocatalytic oxidative desulfurization showed that the oxidation products of sulfur-containing compounds included sulfones and sulfoxides.In addition,the catalyst showed better performance of recycling,and the activity was not decrease obviously after 6 cycle experiments.(2)An imidazole-phosphotungstic acid based ionic liquid catalyst containing carboxylic acid functional group was prepared by ion exchange method at room temperature.Through the elemental analysis,¹H NMR,FT-IR,TG,UV-vis DRS,XRD,XPS and other characterization methods to analyze the structure of the prepared catalyst and proved that the Keggin structure was retained.Experiments results showed that the optimum reaction conditions for the photocatalytic desulfurization system:0.04 g of catalyst,1 m L of[Omim]PF₆,1 m L of formic acid,1 m L of H₂O₂.Under the optimal reaction conditions,the removal rate of dibenzothiophene in the model oil can reach 99.1%at a short time.ESR and free radical scavenging experiments showed that there were many active substances in the photocatalytic system under visible light irradiation.Further more,GC-MS analysis of the products of the extraction coupled photocatalytic oxidative desulfurization showed that the oxidation products of sulfur-containing compounds were mainly the corresponding sulfones.In addition,the catalyst showed better performance of recycling,and the activity was not decrease obviously after 6 cycle experiments.(3)Quaternary ammonium-phosphotungstic acid based ionic liquid catalyst was successful prepared by using hexadecyltrimethylammonium chloride and phosphotungstic acid as raw materials.After a series of characterization methods such as FT-IR,elemental analysis,UV-vis DRS,XRD,TG,XPS and others proved that the Keggin structure was successfully retained in the catalyst.Under visible light radiation,the influence of each component in the photocatalytic system for the desulfurization performance was systematically studied.The reaction conditions of the photocatalytic desulfurization activity experiment were investigated,such as the amount of formic acid,the amount of extractant,the amount of H₂O₂,the influence of different sulfur-containing compounds and fuel composition.Under the optimal reaction conditions,the removal rate of dibenzothiophene in the model oil can reach99.1%at a short time.ESR and free radical scavenging experiments showed that there were many active substances in the photocatalytic system under visible light irradiation.And further more,GC-MS analysis of the products of the extraction coupled photocatalytic oxidative desulfurization showed that the oxidation products of sulfur-containing compounds were mainly the corresponding sulfones.In addition,the catalyst showed better performance of recycling,and the activity was not decrease obviously after 6 cycle experiments.