Silica-pillared clay derivatives using aminopropyltriethoxysilane

Silica pillared montmorillonite has been synthesized using aminopropyltriethoxysilane (APTS), the organic part of which is removed upon calcination. A good intercalation has been established as determined by X-ray diffraction, thermogravimetric analysis and fourier-transform infrared measurements. The concentration of the APTS solution has an influence on the density of the pillars in the interlayer space. In case of enhanced APTS concentration, a material with lower surface area and pore volume is obtained, due to the clay interlayer space being completely occupied by silica pillars. Therefore a templated synthesis method is applied in order to reduce the density of the pillars between the clay sheets. By a pre-intercalation of the clay with cetyltrimethylammonium ions prior to the modification with APTS, the clay sheets are driven apart allowing a more easy intercalation of the APTS molecules. Analysis results show an increase in interlayer free spacing (IFS) to a value of 7.4 Angstrom probably due to the insertion of two layers of silica (-Si-O-Si-) between the clay sheets. A maximal surface area of 252 m(2)/g and a micropore volume of 0.072 cc/g can be obtained in case of the templated synthesis method.