Chemistry in the Confined Space：tudy of Phase Transition of Supercooled Water and Catalyticpplications of Mesoporous Vanadiumsilicate

Because of the amorphous nature of the pore wall, MCM-41 and MCM-48 have weaker acidity and much less hydrothermal stability than conventional zeolites. This limits their application. In this thesis, we improve the stability of pore structure and acidity by using pre-formed Beta zeolite seeds as silica source. On the other hand, using various hydrophobic chain length of cetyltrimethylammonium bromide (C10~C16TAB), hydrothermal temperature (100℃~150℃), and procedure (once or twice hydrothermal method); we derive hexagonally ordered aluminosilicate (MCM-41-S) with narrow pore size distribution in the super-microporous range (less than 2.0nm ). Furthermore, the catalytic application of the solid acid catalysts (MCM-48-S) was demonstrated. In the conventional way, mesoporous carbon (CMK-1) was obtained by impregnation of sucrose on MCM-48 followed by dehydration with concentrated sulfuric acid. Because of the strong acidity of MCM-48-S, CMK-1 could be synthesized without sulfuric acid. The synthesized mesoporous carbon has high surface area (~1500 m2/g) smaller pore size (1.2nm). Cramming water molecules into a tiny space, with a diameter less than 1.5nm, allowing water to remain liquid at a much lower temperature ( -100℃). The non-freezing behavior could be seen for ordered porous silica and carbon. We observed doublet meting peak from water confined in porous carbon by LT-DSC, but only one peak in silica substrate. This may come from more hydrophobic surface of carbon than silica. We also investigate the oxidizing of vanadium catalysts in the confined space. By changing the particle size and pore orderity of mesoporous silica as support. We discovered nano-sized support has faster conversion rate, and higher selectivity for support with ordered pore structure.