Study On Catalytic Oxidative Desulfuriztion Activity Of Loaded Heteropoly Acids/SiO₂ Microporous Materials

Because of more and more strict criterion of sulfur content in fuel by the world, desulfurization technology gets more attention from people. Hydrodesulfurization (HDS) requires large investment, high energy consume, severe operation condition and low activity to some special compounds such as species of thiophenes. Oxidation desulfurization attracted attention from people since 30 years ago thanks to the higher desulfurization activity at low temperature and common pressure, and good efficiency to remove organic sulfurs which HDS can not do.Heteropoly acids are Lewis-acid and proton-acid meanwhile. Due to their possession of good acidity and oxidate catalyst activity, enviromental friendly, HPAs win much attention from researchers. The article uses traditional ether extraction-strong acidification method to synthesize three kinds of molybdovanadophosphoric acids: H₄PMo₁₁VO₄₀, H₅PMo₁₀V₂O₄₀, H₆PMo₉V₃O₄₀. Synthesized compounds were characterizated by FT-IR, XRD and ICP elemental analysis to identify the Keggin structure and atom composition. Dibenzothiophene (DBT) was dissolved in n-octane to produce simulated gasoline in which 500μg/g sulfur contained. Three acids were used to remove the DBT as catalyst, oxidated by H₂O₂, 20ml CH₃CN as extraction solvent, octadecyl trimethylammonium bromide as phase transfer catalyst at different temperature and reaction time. HPLC was performed to check the conversion of DBT. PMo₁₁V, PMo₁₀V₂, PMo₉V₃ had conversion of 85.8%, 35.7%, 10.0% respectively.With TEOS and HPAs as inorganic source and with triblock copolymer Polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO, Pluronic p123) as template, six species microporous HPAs/SiO₂ were synthesized by evaporation-induced self-assembly method. XRD, FT-IR, N₂ adsorbed experiment were performed to review structure of the material. The self-made HPAS/SiO₂ were used to the oxidation of DBT as catalysts to examin their desulfurization activity. The result revealed that the conversion of DBT reached 100% when HPW/SiO₂, HPMo/SiO₂, PMo₁₁V/SiO₂ was added respectively. They showed higher activity than only HPAs were used. The desulfurization rate was 75.5%, 45.6%, 10.5% when HSiW/SiO₂, PMo₁₀V₂/SiO₂, PMo₉V₃/SiO₂ was used respectively. The desulfurization rate remained consistant when the catalysts were five times used repeatedly. By the way, we also examined the reaction conditions' influence to the catalytic activity. The ratio of O/S was chief factor which affectes the desulfurization rate. When O/S=12, the conversion reached peak value. Conversion got higher in the case of longer time and higher temperature.The article discussed the mechanism of generation of the SiO₂ loaded HPAs microporous materials. The Liquid crystal templating mechanism regards that the surfactant which has hydrophilic and hydrophobic groups meanwhile generates spherical micelle and then clubbed micelle. Ordered liquid crystal generates in which HPAs were embodied as the concentration gets thick enough. Template is calcined to produce the HPAs embodied microporous materials.