Synthesis Of Hierarchical Porous Phosphotungstic Acids Catalysts And Its Catalytic Performance In Oxidative Desulfurization

Development of high-quality catalysts for deep oxidative desulfurization is a key issue for solving the atmospheric pollution and upgrading the fuel technologies in our country.The heteropoly acids with hierarchical porous supports have been synthesized using polystyrene?PS?microspheres and block copolymers?P123?as templates.Structure and properties of catalyst were characterized with powder X-ray diffraction,Fourier transform infrared,nitrogen sorption,scanning electron microscopy,transmission electron microscopy and diffuse-reflectance UV-vis spectroscopy.The catalytic performances of the hierarchical porous catalysts were tested through the oxidative desulfurization?ODS?process of dibenzothiophene?DBT?model oil.The main research contents and innovation points are as follow:?1?Macroporous HPW/SiO₂ catalysts were synthesized by sol-gel and colloidal crystallization method using polystyrene as templates and tetraethyl orthosilicate as a silicon source.The synthesized materials possessed hierarchical porous architectures consisting of ordered macropores of³45 nm and of⁸ nm disordered mesopores,with Keggin type HPW embedded in the porous framework.The catalysts had a specific surface area of 238.7²88.1 m²/g.With presenting of HPW/SiO₂ catalyst with 20 wt.%HPW,the removal rate of DBT could reach as high as 99.4%?catalyst dosage 0.1 g,oxygen to sulfurmolar ratio=12,60 ^oC,reaction time 2 h?.The catalyst could be recycled seven times without significant loss of catalytic activity.The excellent recyclabilitywas attributed to the strong interaction between the silic and the HPWspecies.?2?Order Meso/Macroporous HPW/SiO₂ catalysts were synthesized by dual templating using both polystyrene and surfactants and as a silicon source.The synthesized materials possessed hierarchical porous architectures consisting of ordered macropores of 260 nm and of 4.8⁵.0 nm disordered mesopores,with Keggin type HPW embedded in the porous framework.The catalysts had a specific surface area of 320.7³58.1 m²/g and a pore volume of 0.40⁰.45 cm³/g.With presenting of HPW/TiO₂ catalyst with 20 wt.%HPW,the DBT could be completely removed?catalyst dosage 0.1 g,oxygen to sulfurmolar ratio=12,60 ^oC,reaction time 2 h?.The catalyst could be recycled seven times without significant loss of catalytic activity.The excellent recyclabilitywas attributed to the strong interaction between the silic and the HPWspecies.?3?Meso/Macroporous HPW/TiO₂ catalysts were synthesized by sol-gel and colloidal crystallization method using polystyrene as templates and tetrabutyl titanate as a titanium source.The synthesized materials possessed hierarchical porous architectures consisting of ordered macropores of³00 nm and disordered mesopores of¹0.8 nm,with Keggin type HPW embedded in the porous framework.The catalysts had a specific surface area of 68.7⁷7.6 m²/g.With presenting of HPW/SiO₂catalyst with 20 wt.%HPW,the removal rate of DBT could reach as high as 99.8%?catalyst dosage 0.05 g,oxygen to sulfurmolar ratio=4,60 ^oC,reaction time 1 h?.The catalyst could be recycled five times without significant loss of catalytic activity.The excellent recyclabilitywas attributed to the strong interaction between the titania and the HPWspecies.?4?Meso/Macroporous HPW/TiO₂ catalysts were synthesized by sol-gel and colloidal crystallization method using both polystyrene and surfactants as templates.The synthesized materials possessed hierarchical porous architectures consisting of diordered macropores of¹80 nm and ordered mesopores of 5.1⁵.9 nm,with Keggin type HPW embedded in the porous framework.The catalysts had a specific surface area of 190.5²03.6 m²/g and a pore volume of 0.224⁰.326 cm³/g.With presenting of HPW/TiO₂ catalyst with 20 wt.%HPW,the DBT could be completely removed?catalyst dosage 0.05 g,oxygen to sulfurmolar ratio=4,60 ^oC,reaction time1 h?.The catalyst could be recycled five times without significant loss of catalytic activity.The excellent recyclabilitywas attributed to the strong interaction between the silic and the HPWspecies.?5?The objective of this work is to investigate that the effects of catalyst support on desulfurization of fuel.The catalytic activity followed the order:HPW/TiO₂>HPW/SiO₂>HPW/CeO₂>HPW/Al₂O₃>HPW/C.This high performance of the HPW/TiO₂ can be attributed to its excellent adsorption and desorption capacity,which are 1.55 and 0.44 mg S/g,respectively.The low catalytic activity of both HPW/Al2O3 and HPW/C is attributed to higher adsorption capacity than other catalysts.Sulfide is difficult to desorb from the catalyst surface.HPW/TiO₂-CeO₂-10catalyst showed much better catalytic active DBT than both HPW/TiO₂ and HPW/TiO₂-CeO₂-20.The main reason is that HPW/TiO₂-CeO₂-10 proved beneficial to sulfur adsorption capacity when compared to HPW/TiO₂ and HPW/TiO₂-CeO₂-20.Recycling of the HPW/TiO₂-CeO₂-20 catalyst indicates the decrease of the activity of the reused catalys.