NMR Study of Pore Surface and Size in a Mesoporous Material FSM-16 |
| |
Authors: | XIE Xiu-Lan HAYASHI Shigenobu |
| |
Affiliation: | 1. Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 35032, Marburg, Germany;2. National Institute of Materials and Chemical Research, 1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan |
| |
Abstract: | Surface structure, pore size distribution and pore wall thickness of a mesoporous material FSM-16 have been studied by X-ray powder diffraction (XRD), lH and 29Si MAS NMR and 1H liquid-state NMR, and by applying surface silylation as a probe. Concentrations of surface hydroxyl groups for FSM-16 are estimated from 29Si and 1H MAS NMR, which are about 3×l021 g-1, corresponding to approximately 3 nm-2. O2 molecules contribute to 29Si spin-lattice relaxation of Q2 and Q3 as well as Q4, suggesting thin wall thickness. 1H MAS NMR spectra indicate the presence of isolated and hydrogen-bonded hydroxyl groups. Both hydroxyl groups are silylated, where the silylated fraction is about 50%. The spatial distribution of surface hydroxyl groups is estimated from the line width in 1H static spectra. A rather homogeneous distribution is demonstrated in one of the samples. The sample with less homogeneous distribution has a larger affinity for moisture. Pore size and pore wall thickness were determined by 1H NMR measurements on water saturated FSM-16 samples, which are in good agreement with literature values obtained by N2 adsorption isotherms and transmission electron micrographs on a similar sample. In benzene saturated samples, a non-freezing surface layer of benzene is much thicker than that of water, which indicates a stronger interaction between benzene and the FSM-16 surface. |
| |
Keywords: | |
|
| 点击此处可从《高等学校化学学报》浏览原始摘要信息 |
|
点击此处可从《高等学校化学学报》下载全文 |
|