Synthesis And Characterization Of POM-based Materials With Their Application In Oxidative Desulfurization Of Fuel

With increasing environmental pollution, the reduction of the sulfur content in diesel oil becomes an urgent requirement. Sulfur in transportation fuels is a major source of air pollution from automobiles, and the increasingly stringent fuel specifications worldwide also require reducing the sulfur content to a low level. The conventional process for the removal of most sulfur compounds in industry is known as hydrodesulfurization (HDS), which is highly efficient in removing aliphatic and acyclic sulfur-containing compounds, but less effective for aromatic organosulfur compounds such as dibenzothiophene (DBT), benzothiophene (BT). Therefore, alternative deep desulfurization technologies have attracted worldwide attention. Deep desulfurization of organic sulfur compounds in diesel under mild conditions has always been a rather significant subject in the past decades, especially oxidative desulfurization process with hydrogen peroxide.In this paper, a series of POM-based materials were synthesized and employed in the oxidative desulfurization process. These resulting materials were characterized by XRD, IR, Raman, SEM, TEM, BET, DRS and catalytic activity test, and the relationship between the structure of materials and the catalytic activities were also discussed in detail.POM-based hybrid materials HPW-CeO2have been synthesized and characterized by XRD, TG-DSC, SEM, Raman, IR, DRS, and BET analysis. Combined with [C8mim]BF4, the catalyst was very efficient on the removal of DBT by using H2O2as the oxidant under mild Reaction conditionss, which could reach a sulfur removal of99.4%. The amount of catalyst, O/S molar ratio, reaction time and temperature were evaluated in detail, and the favorable operating condition was obtained as well as the kinetic study of substrates. A mechanism was proposed to investigate the oxidation process of DBT.Mesoporous materials WO3-SiO2with different W contents were prepared from [C16mim]3PW12O40by direct sol-gel method and used in the oxidative desulfurization process. The materials were characterized by XRD, FT-IR, Raman, BET, DRS and SEM. The characterization results reveal that WO3was highly dispersed into silica matrix. The materials possessed high surface area (434-713m2/g), pore volume (0.35-0.50cm3/g), and pore size (2.98-4.00nm). The amount of catalyst, O/S molar ratio, reaction time and temperature on catalytic activity were evaluated in detail. Under the optimal conditions (temperature=60℃, O/S=2.5, time=30min), the desulfurization for of dibenzothiophene could reach100%. These materials were found to be highly active and reusable for oxidative desulfurization of bulky organosulfur compound DBT.A series of tungsten-containing mesoporous WO3-SiO2have been successfully synthesized using [C16mim]3PW12O40and [C16mim]Br as co-templates by one-pot and dual-template procedure. The mesostructure and local environment of tungsten species were characterized by XRD, XPS, TEM, FT-Raman, FT-IR, DRS, and BET analysis. The materials possessed high surface area (630-930m2/g), pore volume (0.73-1.00cm3/g), and pore size (4.00-5.36nm). These materials presented a high dispersion of tungsten species and excellent catalytic activity on the removal of sulfur compounds without any organic solvents as extractants. The catalytic performance on different sulfur compounds was also investigated in detail. Under the suitable conditions (temperature=60℃O/S=2.5, time=25min), the desulfurization for of dibenzothiophene could reach100%. The absorptive oxidative desulfurization system could be recycled for nine times without significant decrease in activity. According to the GC-MS analysis of the oxidized products, a mechanism was proposed for the absorptive oxidative process of DBT.Highly ordered mesoporous materials MoO3-SiO2was prepared from [C16mim]3PMo12O40by direct sol-gel method and characterized by XRD, TEM, BET, FT-IR, Raman and DRS. The characterization results revealed that Mo species were introduced into the meso-SiO2framework without effecting its mesoporous structure. These materials exhibited pore volume (0.38-0.44cm3/g) and pore diameter (2.79-4.19nm). The material was found to be highly active and reusable catalyst for oxidative desulfurization (ODS) of organosulfur compounds and desulfurized 99.7%of dibenzothiophene in40min under the mild reaction conditions of temperature=60℃and O/S=2.5.Mesoporous hybrid materials MoO3-SiO2were synthesized by using [C16mim]Br and [C16mim]3PMo12O40as co-templates coupled with hydrolysis tetraethoxysilane (TEOS). XRD, BET, TEM, DRS, FT-IR and Raman were employed to characterize the mesoporous hybrid materials. These materials exhibited reflections corresponding to a pore volume of0.91-1.31cm3/g, a uniform pore size of3.82-4.86nm and large surface areas of834-932m2/g. These materials presented a high dispersion of Mo species and excellent catalytic activity on the removal of sulfur compounds DBT without any organic solvents as extractants. The desulfurization for of dibenzothiophene could reach98.4%in30min under the reaction conditions of temperature=60℃and O/S=2.5.