Abstract
129Xe nuclear magnetic resonance (NMR) spectroscopy was used to investigate the microporous structures of SiO2-TiO2 sol pillared clays. The chemical shift of xenon adsorbed in the pillared clays was measured as a function of xenon pressure on the samples prepared by air-drying followed by calcination at temperatures of 200°-500°C. From the chemical shifts extrapolated to zero pressure, the pore diameters were determined to be 1.0-1.04 nm, which is much smaller than the expansion of the basal spacing of about 3 nm by the pillaring, and rather comparable to the dimensions estimated from a nitrogen adsorption study. As for the pillared samples prepared by a supercritical drying, the 129Xe NMR measurement gave a chemical shift corresponding to the pores having an average diameter much larger than those of the air-dried samples.
