抄録
A new type of mesoporous membranes and films from a material with periodic structure has been developed. A membrane made of MCM-48 with a three-dimensional pore structure was deposited on a porous alumina support under hydrothermal conditions. The silylation with trimethylsilane and triethylsilane was used to enhance hydrothermal stability and hydrophobicity of the MCM-48 membrane. The silylated MCM-48 membranes were used for the separation of ethanol (EtOH), methylethylketone (MEK), and ethylacetate (EA) in aqueous solution. The separation factor and the flux were higher in the order: EA (351) > MEK (201) > EtOH (11) at 30℃, which was related to the hydrophobicity of organic molecules. Furthermore, the hydrothermal stability of the MCM-48 membrane was improved by the silylation. The mesoporous Zr containing MCM-48 (Zr-MCM-48) membranes were synthesized on a porous alumina support. The Zr-MCM-48 membranes are stable in the alkaline solutions at pH 9-12. A small amount of Zr in the MCM-48 effectively enhanced structural stability in alkaline solutions. The Kelvin diameter of the Zr-MCM-48 was estimated to be about 2.5 nm from the permporometry measurement. From the filtration results, the Zr-MCM-48 has very a narrow pore size distribution and MWCO of about 3800 Da which corresponds to ca. 2.3 nm in size. Mesoporous silica films have conventionally been prepared by liquid deposition methods. On the contrary, we have demonstrated a vapor phase synthesis to prepare ordered mesoporous silica films. In this method, the surfactant films were exposed to tetraethoxysilane (TEOS) vapor. We have found nano-phase transition of surfactant-silicate composites under vapor infiltration of TEOS. The phase transition of the nanocomposites under vapor infiltration implies their high mobility in the absence of solvent. When triblock copolymer was used as a surfactant, the silica thin films with two-dimensionally connected cage-like mesopores were formed. The films show lower concentration of residual Si-OH group compared to the film prepared by a conventional sol-gel method. The films show high thermal stability up to 1000℃ and high hydrothermal stability. The vapor-phase synthesis can be applied for organicinorganic nanocomposites and mesoporous metal oxides other than silica and provides opportunities for the creation of new materials technologies.
