Synthesis Of Mesoporous Materials By Tungsten-based Polyoxometalates Ionic Liquids And Study On Catalytic Oxidative Desulfurization In Fuel

SO_x produced by combustion of sulfide in fuel is one of the major pollutants in the atmosphere and the main reason for the formation of acid rain.Deep desulfurization of fuels can control pollution from the source,and it has become one of the key and hot research topics in the petroleum industry,which is important application value and practical significance.In this paper,a series of tungsten-containing mesoporous materials were synthesized by using polyoxometalates based ionic liquid as template and metal source,and they were applied to oxidative desulfurization system.The removal effect of various thiophenic sulfides in fuel was studied,and the mechanism of catalytic oxidation desulfurization was further discussed.The results of this study are as follows:1.A series of WO₃-TiO₂ catalysts([C₁₈H₃₇N?CH₃?₃]₃PW₁₂O₄₀ served as template and tungsten source,Ti?OBu?4 served as titanium source)with a pore structure were successfully synthesized using a hydrothermal treatment method combined with calcination at different temperatures.The composition and morphology of the catalysts were studied though various characterization methods.The mesoporous structure was characterized by TEM and N2 adsorption-desorption isotherms.The XRD and Raman spectra demonstrated that WO₃ was highly dispersed on the surface of the mesoporous catalyst.Meanwhile,the prepared WO₃-TiO₂ catalysts were applied in the oxidative desulfurization?ODS?system.The effects of different reaction conditions on the removal of dibenzothiophene?DBT?and its derivatives were systematically investigated.When 550-WO₃-TiO₂ was employed as catalyst,the removal of DBT could reach 100% with 0.04 g catalyst in 60 min while the n?O/S?is 4 at 50 oC.The sulfur removal of four different sulfur-containing substrates decreased in the following order: DBT > 3-MBT > BT > 4,6-DMDBT.Gas chromatography-mass spectrometer?GC-MS?measurements were employed to investigate the reaction mechanism,DBT sulfone?DBTO₂?was proved to be the only oxidation product of DBT after the reaction.Moreover,the recycling performance of the catalyst was investigated and after recycling for 6 times,the oxidation of DBT could still achieve a high removal of 96.7% without obvious decrease.2.The mesoporous zirconia material containing highly dispersible tungsten species was synthesized by using different carbon chain polyoxometalates ionic liquids as template and tungsten source,and tetrabutyl zirconate [Zr?OBu?4] as zirconium source with calcination at different temperature.The composition and morphology of catalysts were discussed though various characterization methods.The mesoporous structure was characterized by small angle XRD,TEM and N2 adsorption-desorption isotherms.The wide angle XRD,Raman and SEM demonstrated that WO₃ was highly dispersed on the surface of the catalyst.Meanwhile,the synthesized catalysts with different carbon chains and different calcination temperatures were studied in oxidative desulfurization system.The optimum catalyst was 700-C16-WO₃-ZrO₂.The results showed that when the reaction temperature was 50 oC,the molar ratio of oxygen to sulfur was 3 and the amount of catalyst was 0.03 g,the desulfurization rate reached 100% after 60 min.The desulfurization performance of catalysts for different sulfur-containing substrates?DBT,BT,3-MBT,4,6-DMDBT,4-MDBT?were investigated and the order of activity was DBT > 3-MBT > 4-MDBT > BT > 4,6-DMDBT.The mechanism of oxidation desulfurization was also discussed.In the reaction process,the active intermediates of tungsten peroxide were produced with the help of H2O₂ and DBT sulfone?DBTO₂?was proved to be the only oxidation product of DBT after the reaction.In addition,the recycling performance of the catalyst was investigated and after recycling for 6 times,the oxidation of DBT could still achieve a high removal of 96.8% without obvious decrease.3.The catalysts([C₁₆mim]₄SiW₁₂O₄₀ served as template and tungsten source,tetraethylorthosilicate served as silicon source)with a mesoporous structure were successfully synthesized by a sol-gel method combined with calcination at different temperature.The composition and morphology of catalysts were studied though various characterization methods.The mesoporous structure was characterized by small angle XRD,TEM and N2 adsorption-desorption isotherms.The wide angle XRD,Raman and TEM demonstrated that WO₃ was highly dispersed on the surface of the catalyst.Meanwhile,the synthesized catalysts were studied in oxidative desulfurization system,it was found that when the catalyst calcined at 550 oC,the removal of 4,6-DMDBT could reach 100% with 0.015 g catalyst in 70 min while the n?O/S?is 3 at 60 °C.The sulfur removal of DBT,4-MDBT,3-MBT and BT could also reach 100% by extending the reaction time,indicating that the catalyst had excellent catalytic performance.The sulfur removal of different sulfur-containing substrates decreased in the following order: DBT > 4-MDBT > 3-MBT > BT.In addition,GC-MS measurement was employed to investigate the reaction mechanism,and 4,6-DMDBT sulfone?4,6-DMDBTO₂?was proved to be the only oxidation product of 4,6-DMDBT after the reaction.Recycling experiments showed that the removal of 4,6-DMDBT remained 100% after 6 cycles of the catalyst.