Study Of Defective Metal Oxide On The Removal Of Aromatic Organic Sulfur In Fuels

In recent years,the pollution caused by the development of cities has become increasingly serious.The combustion of gasoline and diesel with high-sulfur concentration will bring about a large amount of sulfur oxides（SO_x）,causing acid rain and destroying the ecological environment.The ultra-deep desulfurization of fuel oil is of great significance to the production of clean fuel oil,and can inhibit the generation of sulfur oxides from the root cause,and solve many environmental pollution problems caused by the combustion of sulfur-containing fuel oil.The metal oxide desulfurization catalyst is stable in structure,easy to be compacted and has abundant metal catalytic sites.Therefore,it exhibits excellent properties in the catalytic oxidative desulfurization reaction.However,the inherent hydrophilicity of the metal oxide makes it faced the problem of poor affinity and mass transfer efficiency.Thus,it is easy to cake and adherend during the reaction,resulting in an increase in material usage and energy consumption.In addition,the dense crystallization weakens the exposure of accessible active metal sites in metal oxides,further limiting the industrial application of metal oxides in desulfurization.In response to this problem,this paper first tries to modify metal oxides and introduces a large number of defect sites to construct the interface modified defect metal oxides,catalyzing the removal of organic sulfur in fuel oil.The main achievements are as follows:1.Developing interface modification strategies to successfully graft oleylamine molecules on the surface of tungsten oxide.Then,acid treatment strategy to control the synthesis of amphiphilic catalyst containing defects.Analyzing the structure and composition of the catalyst surface through various spectroscopy techniques.The results show that when the catalyst were coated with oleylamine molecules,the dispersibility in the oil phase is significantly improved.It exhibits excellent catalytic oxidative desulfurization performance.At a reaction temperature of 333 K,the dibenzothiophene can be completely oxidized after 40 min of reaction.A quasi-in-situ spectroscopy experiment was conducted to study the active species of the reaction.It is proved that the surface oxygen vacancies of tungsten oxide interact with hydrogen peroxide to produce tungsten peroxide species,revealing the catalytic mechanism of the catalytic oxidative desulfurization process.2.In view of the characteristics of heterogeneous catalytic oxidative desulfurization reaction,a solid phase modifier is developed to modify the tungsten oxide interface.At the same time,the tungsten oxide is doped with molybdenum sites to realize the synthesis of a highly dispersible and active tungsten oxide catalyst.The composition,structure and morphology of the catalyst were analyzed through a variety of characterization methods.At a reaction temperature of 333 K,compared to the bared tungsten oxide catalyst,the target catalyst not only shows a conversion rate of 96.4%for the dibenzothiophene,but also shows a significant improvement in cycle stability.Also,the catalyst shows excellent removal performance of organic sulfur in real diesel and the removal rate can reach 95.7%within 1h.3.The weak reducibility and defect sites on the surface of defective tungsten oxide are used to stabilize and disperse platinum species.The structure and formation mechanism of the catalyst were discussed by transmission electron microscopy,ultraviolet-visible diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy.Model construction and calculations is used in explaining the stability and dispersion of platinum species on the support.The activity experiment confirme that the catalyst shows the ability of activating molecular oxygen to catalyze the deep desulfurization of fuel.When the platinum loading in the catalyst is 0.8%,the conversion rate of dibenzothiophene reaches more than 99.0%（the reaction temperature is 393 K,the reaction time is 4 h）.The polar product sulfone can be completely removed by extraction.At the same time,the catalyst regeneration performance is relatively stable.4.Developing a lattice reconstruction strategy introduces lattice defects and oxygen vacancies into metal oxides.To understand the calcination process,the thermogravimetric-differential scanning calorimetry analysis of catalysts were carried out,clarifying the etching mechanism on the surface of metal oxides.The defect status on the catalyst was characterized.Furthermore,it is clarified that this strategy not only increases the specific surface area of the defective catalyst,but also enhances the catalytic oxidative desulfurization performance.The conversion rate of defect-containing titanium oxide to dibenzothiophene is 3.7 times than that of ordinary titanium dioxide.It is proved that the active intermediate species is superoxide radical.5.Small size defective titanium oxide derived from two-dimensional titanium carbide is developed and used to catalytic oxidation desulfurization.Using the rich interlayer porous structure and characteristics of two-dimensional titanium carbide,the experimental conditions are controlled to grow defective titanium oxide at its interface.It is clarified that the interface interaction between molecular oxygen and two-dimensional titanium carbide is the key to the dynamic generated of titanium oxide during the reaction.The activated and the used catalyst were further characterized.It show that the defective titanium oxide is very important.The catalytic oxidation performance is significantly improved by pre-active titanium carbide as a catalyst.When the reaction temperature was 393 K and the amount of catalyst was 1 mg,the DBT conversion reached 100%at 80 min.In the process of the reaction,molecular oxygen is continuously activated,generating abundant free radical species,which is the key to the conversion of dibenzothiophene.