Bi₂WO₆-based Supported And Heterojunction Photocatalytic Oxidative Desulfurization Catalyst

The supported Bi₂WO₆/BMMS catalyst was prepared by using Bi₂WO₆as the active component and double mesoporous silica?BMMS?as the carrier.The TiO₂-Bi₂WO₆ heterojunction catalyst was prepared by using TiO₂ and Bi₂WO₆.The catalyst was characterized by XRD,N₂ adsorption and desorption,FTIR,UV-vis,SEM,EDS and TEM.The dodecan and dibenzothiophene?DBT?were used as solvents and solute to form a simulated oil,and the simulated oil was used as a raw material to evaluate the photocatalytic oxidative desulfurization?PODS?activity of the catalyst,and the catalyst after the reaction was recycled and reused.The re-use performance and the photocatalytic oxidation desulfurization mechanism of the two catalysts were proposed respectively.The main research results are as follows:?1?Bi₂WO₆ was successfully loaded onto the molecular sieve BMMS and maintained the ordered double mesostructure and wheat spike morphology of BMMS.Compared with Bi₂WO₆,Bi₂WO₆/BMMS has a larger specific surface area.Bi₂WO₆/BMMS catalysts exhibit good PODS performance compared to Bi₂WO₆/SBA-15 because BMMS contains two pores of different pore sizes,in which the mesopores of the large pores play a role in transport and the molecules are better.The ground diffusion allows the reactants to reach the pores smoothly,and the mesoporous specific surface area of the small pores is large enough to provide more sites for adsorption and catalytic reaction.The Bi₂WO₆/BMMS catalyst has the highest catalytic activity when the loading of Bi₂WO₆ is 10%.The optimized reaction conditions have an O/S molar ratio of 15:1;the volume ratio of the extractant to the simulated oil is 1:1;and when the amount of the catalyst is 3 wt%,the desulfurization rate can reach 94.7%.After the catalyst is reused 6 times,the desulfurization rate is still close to 90%.Through free radical trapping experiments,it was found that?OH and h⁺are more effective in the PODS reaction than?O^2-.?OH and h⁺are the main reactive groups of PODS.H₂O₂and h⁺have strong oxidizing power to produce more?OH can oxidize DBT and improve PODS.?2?TiO₂ and Bi₂WO₆ were successfully combined to form a heterojunction.After compounding,TiO₂ was an amorphous structure;Bi₂WO₆ was an orthorhombic system,Bi₂WO₆ was a three-dimensional flower-like microsphere structure;TiO₂ particles were present in the nanosheets of Bi₂WO₆ and dispersed throughout in the microsphere sample,the photoresponse range of the TiO₂-Bi₂WO₆ catalyst was broadened compared to Bi₂WO₆ alone.Compared with Bi₂WO₆ and TiO₂,the TiO₂-Bi₂WO₆ catalyst showed good PODS performance because Bi₂WO₆ and TiO₂ produced a synergistic effect,and the formation of an applied electric field effectively inhibited the bonding rate of photogenerated electron hole pairs.When the loading of TiO₂ is 10%,the catalytic activity of TiO₂-Bi₂WO₆catalyst is the highest.The optimized reaction conditions have an O/S molar ratio of 15:1;the volume ratio of the extractant to the simulated oil is 1:1;and when the amount of the catalyst is 3 wt%,the desulfurization rate can reach92.1%.After the catalyst was reused 6 times,the desulfurization rate was still close to 90%.It can be determined by free radical trapping experiments that?O^2-and h⁺are the main active groups,the formation of a heterojunction between the two effectively controls the recombination rate of photogenerated electrons and holes,make full use of light energy,and enhance the PODS effect.