Hierarchical Porous HPW/SiO₂ Catalyst Doped By Metal Oxides For Catalytic Oxidative Desulfurization

Oxidative desulfurization under mild conditions is considered to be one of the most promising methods for deep desulfurization of fuels,especially oxidative desulfurization with heteropoly acids and hydrogen peroxide.The phosphotungstic acid catalysts supported by hierarchical porous materials have been synthesized.Then Ti,Al,Ce doping was employed.And the structure of catalysts were characterized with scanning electron microscopy,transmission electron microscopy powder X-ray diffraction,nitrogensorption,Fouriertransforminfrared,andUV-vis diffuse-reflectance spectroscopy.Then the catalytic performances of the catalysts were tested in an oxidative desulfurization?ODS?process,and the relationship between the structure and properties of catalysts was discussed.The content of thesis contains the following three parts:Firstly,hierarchical porous HPW/SiO₂-TiO₂ catalyst was synthesized by Sol-gel templating metod with polystyrene?PS?and P123 as templates,TEOS as silicon source,TBOT as titanium source.The macropore pore diameter of HPW/SiO₂-TiO₂ is198 nm,while the mesopore of the catalyst is 4.2 nm.The catalyst has a specific surface area of 155.5 m²/g.The removal rate of DBT can reach as high as 100%under a certain condition?20 wt.%HPW,TiO₂/SiO₂ 1:1,reaction temperature 60 ^oC,catalyst dosage 0.1 g,oxygen to sulfur molar ratio 12,reaction time less than 40 min?.The catalytic performance of the hierarchical porous HPW/SiO₂-TiO₂ is much better than that of mesoporous HPW/SiO₂ or hierarchical porous HPW/SiO₂.The catalyst remains its excellent reaction activity when recycled 6 times.Secondly,hierarchical porous HPW/SiO₂-Al₂O₃ catalyst and HPW/SiO₂-CeO₂catalyst were synthesized by self-assembly method and colloidal crystallization templating method with aluminum isopropoxide as aluminum source,cerous nitrate as cerium source,TEOS as silicon source,PS and P123 as templates,respectively.The macropore pore diameter of HPW/SiO₂-Al₂O₃ is 175 nm,while the mesopore of the catalyst is 2.9 nm.HPW/SiO₂-Al₂O₃ catalyst has a specific surface area of 271.5m²/g;the macropore pore diameter of HPW/SiO₂-CeO₂ is 192 nm,while the mesopore of the catalyst is 2.8 nm.HPW/SiO₂-CeO₂ catalyst has a specific surface area of 323.6 m²/g.DBT could be absolutely removed under a certain condition which is 20 wt.%HPW,Al₂O₃/SiO₂ 0.02,reaction temperature 60 ^oC,catalyst dosage0.1 g,oxygen to sulfur molar ratio 12,reaction time 120 min for HPW/SiO₂-Al₂O₃,or20 wt.%HPW,CeO₂/SiO₂ 0.1,reaction temperature 60^oC,catalyst dosage 0.1 g,oxygen to sulfur molar ratio 12,reaction time 90 min for HPW/SiO₂-CeO₂.Two catalysts remain stable when recycled 5 times under operating conditions.Finally,mechanism was explored for the water poison on hierarchical porous laden HPW catalysts,based on the experimental fact.Under the same reaction condition,when the O/S increases,the removal rate of DBT for several hierarchical porous laden HPW catalysts share a phenomenon:first increase and then decrease.H₂O₂ was diluted to start a new reaction,and the activity of catalysts decreased gradually when the multiple of H₂O₂ dilution increased.The adsorption of DBT will be disturbed by water on the surface of the catalysts.At the same time,the existence of water causes agglomeration of catalysts,resulting in the loss of the activity of the catalysts.