Synthesis Of Transition Metal Oxide Supporting On G-C₃N₄ And Study On Catalytic Oxidative Deep Desulfurization In Fuel

The fuel oil consumption has been on the rise with the development of morden industries.The sulfur compounds in fuel oil can be combusted into SOx which will deactivate some catalysts in the vehicle tail gas treatment device,causing excessive emissions of SOx and pollute the environment.Thus,it is essential to remove sulfur compounds in fuel oil.Now,the commonly used hydrodesulfurization?HDS?can remove sulfur compounds in fuel oil,but it needs to be carried out under high temperature and pressure,and has poor activity on aromatic sulfides.Particularly,oxidative desulfurization technology?ODS?has attracted much attention due to its mild conditions and high selective removal of aromatic sulfides.The oxidative desulfurization process is the activation of H2O2 or O2 in the air to oxidize the sulfides to the corresponding oil-insoluble sulfone with the catalysts.In this papaer,graphite-like phase carbon nitride?g-C3N4?was used as the carrier,and different transition metal oxides?WO3,V2O5 and MoO3?were used as active centers to synthesize supported catalysts by a facile“in situ calcination”technique,thus achieving efficient removal of sulfides in fuel oil.The main works are as follows:1.A catalyst of WO₃/few layer g-C₃N₄ was synthesized by a facile“in situ calcination”technique.[(C₁₆H₃₃)₂N?CH₃?₂]₂W₂O₁₁ was used as the precursor of WO₃nanoparticles.Few layer g-C₃N₄ with large surface specific area(203 m² g^-1)obtained through two thermal condensation method was used as the carrier.The composition and morphology of WO3/few layer g-C3N4 were characterized by XRD,FT-IR,XPS,N2adsorption-desorption,SEM and TEM systematically.It was found that WO3nanoparticles highly dispersed on the surface of few layer g-C3N4.Then,the catalytic oxidative desulfurization performance of the support catalyst was investigated in detail.Besides dibenzothiophene?DBT?,two other difficult-to-remove sulfides?4-methyldibenzothiophene?4-MDBT?and 4,6-dimethyldibenzothiophene?4,6-DMDBT??can be removed completely under mild reaction conditions.After the WO3/few layer g-C3N4 was used 6 times,the removal of DBT can still remain 100%.2.A catalyst of V₂O₅/g-C₃N₄ was synthesized by a facile“in situ calcination”technique.NH4VO3 was used as the precursor of V2O5 nanoparticles and g-C3N4 was used as the carrier.The composition and morphology of the V2O5/g-C3N4 catalyst were systematically investigated by various characterization methods,indicating that V2O5was dispersed on the surface of g-C3N4.Then,the catalytic oxidative desulfurization performance of the support catalyst was investigated in detail.The removal of DBT could reach to 96.1%for 6 h under 120°C with O2 in the air,which made the sulfur content in the oil less than 10 ppm.For different sulfur-containing substrates,the order of desulfurization activity was in the following order:DBT>4-MDBT>4,6-DMDBT.ESR characterization and free radical selective quenching experiments were used to find superoxide radicals?O2^-·?during the reaction.After V2O5/g-C3N4 was used for 6times,the DBT removal did not decrease significantly,indicating that V2O5/g-C3N4 has good stability and excellent cycling performance.3.A catalyst of MoO₃/g-C₃N₄ composite was synthesized by a facile“in situ calcination”technique.[?n-C₄H₉?₃NCH₃]₂Mo₂O₁₁ was used as the precursor of MoO₃and g-C3N4 was used as the carrier.The composition and morphology of MoO3/g-C3N4were characterized by a serious of characterization methods systematically,indicating that MoO3 was dispersed on the surface of g-C3N4.Then,the catalytic oxidative desulfurization performance of the catalyst was investigated in detail.The removal of DBT could reach 100%within 100 min under 130°C.Superoxide radical?O2^-·?appeared in the oxidative desulfurization by the analysis of ESR and free radical selective quenching experiments indicating that the catalyst could activate O2 in the air into O2^-·.After the use of MoO3/g-C3N4 for 6 cycles,the oxidative desulfurization performance did not significantly decrease.Gas chromatography-mass spectrometer?GC-MS?characterization revealed that DBT was completely oxidized to the corresponding sulfone species DBTO2.