1H NMR studies of the adsorption of water on silicalite

✍ Scribed by V.V. Turov; V.V. Brei; K.N. Khomenko; R. Leboda

• Book ID: 104431445
• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 217 KB
• Volume: 23
• Category: Article
• ISSN: 1387-1811
• DOI: 10.1016/s1387-1811(98)00067-5

✦ Synopsis

A study has been made of silicalite samples with a specific surface area (by the BET method ) of S=350 m2 g-1 which were synthesized on the basis of fumed silica and did not contain aluminum. 1H NMR spectroscopy is used to determine the value of the chemical shift of the adsorbed water molecules and to characterize the adsorbed water layers. It has been found that in the case of both water vapor adsorption and water adsorption from aqueous suspensions, the volume of silicalite pores occupied by adsorbed water molecules is considerably smaller than the total volume of the pores. The chemical shift of water molecules on the silicalite surface depends on temperature and varies from 4.5 ppm at 330 K to 5.6 ppm at 220 K. The high chemical shift values are attributed to clustering of water molecules in the adsorbent pores, and to the fact that each molecule of the clusters participates simultaneously in the formation of more than three hydrogen bonds.