Influence of water on the pillaring of montmorillonite with aminopropyltriethoxysilane

Silica pillaring of montmorillonite has been carried out using aminopropylt riethoxysilane (APTS) as pillaring precursor. Several synthesis parameters, i.e. reaction temperature, reaction time, concentration of components, etc ., are of importance in this synthesis. However, the concentrations of APTS and H2O under which the hydrolysis is performed have a paramount effect on the molecular structure and the degree of polymerization of the pillaring precursors, and therefore, also on the porosity of the obtained silica inte rcalated clay. X-ray diffraction (XRD) analysis and diffuse reflectance inf rared Fourier transform (DRIFT) spectra reveal that the presence of water i n the system is one of the most important parameters in the reaction sequen ce. These results are refined and confirmed by transmission electron micros copy (TEM). Combining the results of all the applied techniques, two types of APTS interaction with the clay can be observed: internal and external ad sorption depending on the conditions used. Besides the influence of the wat er concentration, the influence of the use of templating ions (cetyltrimeth ylammonium) on the synthesis is also studied. In the case of the templated approach, in which the alkylammonium ions are pre-adsorbed on the clay prio r to the pillaring with APTS, a surface area and a pore volume as high as 4 87 g(-1) and 0.45 cm(3) g(-1) have been obtained.