Increasing the hydrothermal stability of mesoporous SiO2 with methylchlorosilanes—a ‘structural’ study


Castricum, Hessel L and Mittelmeijer-Hazeleger, Marjo C. and Sah, Ashima and Elshof, Johan E. ten (2006) Increasing the hydrothermal stability of mesoporous SiO2 with methylchlorosilanes—a ‘structural’ study. Microporous and Mesoporous Materials , 88 (1-3). pp. 63-71. ISSN 1387-1811

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Abstract:Mesoporous silica gels with various pore sizes are hydrophobised by liquid-phase silylation with mono- and difunctional methylchlorosilanes. Changes in the pore structure as a result of the silylation reactions are monitored in order to assess the distribution of the hydrophobic groups. Extensive polymerisation of dimethyldichlorosilane (DMDCS) causes blocking of the micropore fraction. For silica with pore sizes in the supermicroporous range (2 nm pore diameter), this leads to hydrophobisation of almost exclusively the outer surface. While for trimethylchlorosilane (TMCS) a smaller number of molecules react with the surface, modification is more homogeneous and an open structure is optimally preserved. Both silanes lead to lower surface polarity and increased hydrothermal stability, i.e., preservation of the porous structure during exposure to water. As DMDCS reacts more extensively, this agent would be recommended for ceramics with pore diameters larger than about 6 nm. TMCS is the most suitable agent for pore diameters smaller than 4 nm and in case preservation of micropores is required
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Copyright:© 2006 Elsevier Inc
Science and Technology (TNW)
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