Synthesis And Study On The Photocatalytic Desulfurization Performance Of POMs/Ti-MOFs/g-C₃N₄ Ternary Composite Catalysts

Fuel oil desulfurization technology is of great significance for the production of clean energy.Among many desulfurization technologies,photocatalytic desulfurization technology has attracted much attention of many researchers for its advantages of simple operation,friendly environment and low cost.The photocatalysts play a crucial role in photocatalytic desulfurization.In this paper,a series of POMs/Ti-MOFs/g-C₃N₄photocatalysts have been designed and preparation,and applied in the process of photo-thermal extraction catalytic oxidation desulfurization system（PTECODS）.Firstly,the ternary composite photocatalysts Mo₆/NH₂-MIL-125（Ti）/g-C₃N₄with different molar ratios of Ti:Mo were synthesized by evaporative solvent method.The structure and composition of the composite photocatalysts were characterized by XRD,FT-IR,XPS,SEM,TEM and so on.The light response of the composite catalysts was tested by UV-vis and PL.The catalytic activity and reusability of catalysts were investigated by studying the removal efficiency of thiophene sulfur compounds in PTECODS.Under the optimal reaction conditions:[Bmim]PF₆was used as extractant,C3 with the molar ratio of Ti:Mo of 1:0.5 was used as photocatalysts,the catalyst dosage was 0.03 g,the O/S value was 6:1,and the reaction temperature was 70°C,DBT was almost completely transformed in 60 min.This is because the specific surface area of the composite catalysts increases and leads to more active sites.At the same time,the light absorption capacity and the light response range increase and the photogenerated carriers recombination rate decreases due to the heterojunction structure between NH₂-MIL-125（Ti）and g-C₃N₄.Every component in Mo₆/NH₂-MIL-125（Ti）/g-C₃N₄composite catalysts interacted with each other to improve the efficiency of photo-thermal extraction catalytic oxidation desulfurization.In the cyclic experiment of the composite catalysts,the catalytic activity of catalysts remained above 90%after 8 times.Finally,the result of free radical capture experiment showed that·O₂^-and h⁺were the two main active species,and the desulfurization performance of photo-thermal extraction catalytic oxidation desulfurization was significantly enhanced through the photo-thermal synergistic effect.Secondly,a novel Lindqvist POMs catalysts Mo₆/MUV-10（Mn,Ti）/g-C₃N₄were prepared by impregnation method and applied in PTECODS.The structure,composition,morphology and light responding of the photocatalysts were characterized by XRD,FT-IR,SEM,XPS,UV-vis,PL and so on.The characterization results verified that the structure of MUV-10（Mn,Ti）was not destroyed after loading Mo₆,and Mo₆was uniformly distributed.The results of desulfurization experiments showed that under visible light irradiation,the reaction temperature was 70°C,the O/S value was 4:1,and 0.03 g photocatalysts with the molar ratio of Ti:Mo of 1:6,the photocatalysts M4 showed the highest DBT conversion rate within 40 min,which was almost100%.The interaction among every component of Mo₆/MUV-10（Mn,Ti）/g-C₃N₄promotes the separation of photogenerated electrons and holes.At the same time,the synergistic effect between Mo₆/MUV-10（Mn,Ti）and g-C₃N₄expands the absorption range of visible light of the composite photocatalysts,enhances the separation rate of photogenerated electron-holes and improves the performance of photo-thermal extraction catalytic oxidation desulfurization.In addition,the composite photocatalysts present good recyclability and still maintains certain activity after 3 cycles.Finally,the possible reaction mechanism in the process of photo-thermal extraction catalytic oxidation desulfurization is discussed deeply.