Study On Tungsten-Based Three-Dimensional Ordered Macroporous Materials For Oxidative Desulfurization Of Fuels

The development of economy and industry has brought convenience to life,but also caused environmental problems.SO_x generated by the combustion of sulfides in fuel causes human respiratory diseases and catalyst poisoning in automobile exhaust gas treatment devices.Acid rain formed by SO_x,oxygen and water leads to acidification of water and soil.A series of hazards of SO_x forced the relevant state departments to introduce fuel standards to limit sulfur contenting in fuel.The hydrodesulfurization technology used in the industry can remove sulfides such as mercaptans and thioethers,effectively reducing the sulfur content in the fuel,but the removal of aromatic sulfides such as benzothiophene and its derivatives is not good.Other non-hydrodesulfurization technologies have emerged.Among them,oxidative desulfurization has drawn widely attention due to its simple operation,mild reaction and high desulfurization efficiency.In addition,the 3DOM structure is widely used in the field of catalysis owing to its interconnected pores,large pore size and large pore volume.Firstly,in this paper,the polyacid ionic liquid[C₁₆mim]₆H₂W₁₂O₄₀ was used as the active center and silica was used as the carrier.The catalyst IL-3DOM SiO₂ was synthesized by the colloidal template method with PMMA serving as macroporous template.The successful loading of the ionic liquid in the catalyst was confirmed by FT-IR,XRD and XPS.The 3DOM structure in the catalyst was confirmed by SEM,TEM and BET.The optimal reaction conditions were determined by experiment with H₂O₂ as oxidant:O/S was 3,reaction temperature was 60 ^oC and catalyst dosage was0.02 g.Under the optimal reaction conditions,the sulfur removal of DBT can reach99.9%within 40 min.The desulfurization order of different sulfides was 4-MDBT>DBT>4,6-DMDBT>3-MBT>BT.The sulfur removal was still 94%after 17 times.The catalytic oxidative desulfurization reaction mechanism of IL-3DOM SiO₂ was speculated based on GC-MS and ESR characterization.Secondly,in order to select oxygen as oxidant,the catalyst 3DOM WO_x was directly synthesized to activate oxygen with PMMA serving as macroporous template and ammonium metatungstate as tungsten source.The catalysts 3DOM WO_x-300,3DOM WO_x-400 and 3DOM WO_x-500 were prepared by adjusting the calcination temperature.The crystal form and valence state of the catalysts were proved by Raman,XRD and XPS.The 3DOM structure of the catalysts was characterized by SEM,TEM and BET.The catalytic oxidative desulfurization activity of the catalysts with oxygen as the oxidant was investigated.Under the optimal reaction conditions of120 ^oC and 0.01g,the sulfur removal of 4,6-DMDBT can reach 99%within 4 hours.The desulfurization sequence of the catalyst 3DOM WO_x-400 for different sulfides was 4,6-DMDBT>4-MDBT>DBT.After 6 cycles,the sulfur removal can still reach more than 93%.In addition,the reaction mechanism of the catalyst 3DOM WO_x-400was inferred.Finally,in order to reduce the use of tungsten,the catalytic oxidation desulfurization catalyst 3DOM W-TiO₂ was prepared by using titanium dioxide as the main component and tungsten as a dopant.The catalysts 3DOM TiO₂,3DOM W-TiO₂-30,3DOM W-TiO₂-20,3DOM W-TiO₂-10 and 3DOM W-TiO₂-5 were prepared by adjusting the molar ratio of titanium to tungsten.The successful doping of tungsten in the catalyst was confirmed by XRD,Raman,XPS and other characterizations.The 3DOM structure was proved by SEM,TEM and BET.When the amount of catalyst was 0.01 g and temperature was 120°C,the reaction activity was the best.The sulfur removal of DBT can reach 98%within 6 h.The desulfurization sequence of sulfides was DBT>4-MDBT>4,6-DMDBT.After 4cycles,the sulfur removal was above 95%.Then the oxidation reaction mechanism was presumed.