Chem.
Mater. 1998, 10, 467-470
Synthesis of Ordered Microporous Silicates with
Organosulfur Surface Groups and their Applications as Solid Acid
Catalysts
Myong H. Lim,
Christopher F. Blanford, and Andreas Stein*
<>Department of Chemistry, University of
Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455-0431
Abstract
Mercaptopropyl-functionalized
porous silicates were synthesized by the co-condensation of
mercaptopropyltriethoxysilane (MPTS) and tetramethoxysilane (TMOS) in
the presence of a cationic surfactant under basic conditions. Ordered
hexagonal arrays of channels, similar to those of MCM-41 mesoporous
sieves but with smaller pore diameters, were obtained with MPTS:TMOS
ratios as high as 1:2.5 and a thiol content up to 5 mmol S/g silica.
The extracted solids were microporous, with an average pore diameter of
ca. 14 Å, a surface area of 792 m2/g and a total pore volume of
0.47 cm3/g. The surface thiol groups were demonstrated to be efficient
absorbers of heavy metals, such as mercury ions. Furthermore, it was
possible to oxidize the supported thiol groups to sulfonic acid groups,
thus creating a solid acid ion exchanger or catalyst. The sulfonic-acid
functionalized material was found to be an efficient heterogeneous
catalyst for the protection of alcohols by tetrahydropyranylation.