Synthesis of Surface Covered Solid Acid and Base

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Solid bases of MgO and CaO, and solid superacid of sulfated zirconia were covered with metal oxides which show no or less acidic and basic characters to prepare solid acid and base catalysts showing tolerance to H_2O and CO_2. The oxides of Al, Si, Ti, and Zr were used for covering solid acids and base catalysts. A new preparing technique of surface gelation was applied for covering. This is the technique that a metal alkoxide dissolved in ethyl acetate is decomposed on metal oxide or hydroxide surface by their acid or base properties.MOx/MgO (M=Al, Si, Ti, Zr) and M'Ox/CaO (M'=Al, Si, Ti) were prepared by the developed surface gelation technique. Among the synthesized solid base catalysts, Al_2O_3/MgO, Al_2O_3/CaO, and TiO_2/CaO showed higher catalytic activity for retro-aldol reaction of diacetone alcohol. The solubility of CaO could not be disturbed by covering it with SiO2 bysingle deposition procedures. The elution of Ca^<2+> was strongly inhibited by covering by double deposition method.The sulfated zirconia was covered with zirconium oxide by surface gelation to inhibit the elution of sulfate ion bonded to zirconia surface. However, the inhibition effect was not observed. The catalytic activity was largely increased.