Synthesis Of Magnetic Silica Supporting Fluoroalkylsulfonylimide And Catalysis On Hydration Of Carbonhydrates

Magnetic solid acid can be separated from the reaction system with exeternal magnetic field, very convenient to isolate and recycle, specially in the system with the solid residue remained; Bis[（perfluoroalkyl）sulfonyl]imides is considered as the ideal alternate to sulfonic acid due its excellent thermal, hydrothermal stability, strong acidity.Initially, SiO₂-coated Fe₃O₄ nanoparticles was used as the inner core to graft another silica layer containing strong acid group-- perfluoroalkylsulfonylimide（-SO2NHSO2CF3/C4F9）, then, the target solid acid was obtained. The bounded-SO2NHSO2CF3/C4F9 was imported by prepolymer which containing [（MeO）3Si-] group, prepolymer grafted onto the magnetic silica cores by hydrolysis; and the Fe₃O₄ nanoparticles were protected by the inner silica from being corrosion. Sodium dodecyl sulfate（SDS） was added in the system to make the magnetic silica cores scatterring more uniform. Finally the target solid acid Fe@nSiO₂@ mSiO₂-SSFMI and Fe@nSiO₂@mSiO₂-SSFBI ware prepared.The 3-（trimethoxysilyl）propyl-methacrylate[CH2=C（Me）COO（CH2）3Si（OMe）3] and the 4-Styrene-sulfonyl（perfluoroalkylsulfonyl）imide（p-CH2=CHC6H4SO2NNaSO2CF3/C4F9） reaction by the double bond polymerization to prepare prepolymer, prepolymer grafted onto magnetic cores. The optimal conditions for: TEOS/ prepolymer（mol/mol） = 28.75, magnetic core / prepolymer（g/mol） = 0.5, dispersant as SDS, reaction in 20 ℃ for 20 h, then 2.5 wt % NH3 · H2 O gel quickly. Target solid acids were characterized by FT-IR, pyridine-FT-IR, XPS, TG, TEM, N2 adsorption--desorption, showed that this type of solid acid has high thermal stability（≤229 ℃）and better magnetism（>3.0 emu/g）.Biomass is expected to replace traditional fossil energy, due to its renewable. Cellobiose the same as cellulose has β-1, 4 glycosidic bond, is commonly used template molecule when study glycosidic bond hydrolysis. Fe@nSiO₂@mSiO₂-SSFMI and Fe@nSiO₂@mSiO₂-SSFBI catalyzed cellobiose hydrolysis can get 80%- 91% glucose yeild, respectively recycle 3 times and 4 times at high temperature（130℃） and high pressure, proving that solid acids have good hydrothermal stability. Then solid acid and cellulose was mixed and ball milled, then hydrolysis in 130℃ for 2h, when the ball milling condition was 150 rpm/min for 24 h, glucose yeild was 30.5%, catalyst recovery was 37.6%.